List of business routes of the Interstate Highway System

The Interstate Highway System of the United States, in addition to being a network of freeways, also includes a number of business routes assigned by the American Association of State Highway and Transportation Officials (AASHTO). These routes connect a central or commercial district of a city or town with an Interstate bypass.

As the main purpose of these routes are to serve a certain downtown area, business Interstates are typically routed along surface roads. These routes do not have to meet Interstate Highway standards and are not considered part of the Interstate Highway System. AASHTO does, however, apply similar standards as to new U.S. Highways, requiring a new business Interstate to meet certain design standards.

Business Interstates are more commonly found in the western regions of the United States, as well as both across the Great Plains and in the state of Michigan. In contrast, Eastern states generally did not designate as many business Interstates. This geographic difference can be attributed to the way the Interstate Highway System was constructed in different parts of the country. In many eastern states, the new Interstates were often built to parallel the existing U.S. Highway network, rather than directly replacing those older routes. With the exception of mountainous areas, this left the majority of U.S. Highways intact, or co-signed routes with the Interstates. However, in the western states, the construction of the Interstate system more frequently involved directly overlaying the former U.S. Highway alignments. This sometimes left sections of the old U.S. Highways disconnected, especially in rural areas between cities and towns. To maintain access to those former highway segments, business Interstate designations were often applied as a way to guide drivers to key commercial districts and services. Although business Interstates are primarily found along primary Interstates, a few auxiliary Interstates also have their own business route designations.

Like auxiliary Interstates, business Interstates can be repeated from state to state along their route. The only difference is that business Interstates can also be repeated in several locations within the same state.

Terminology and guidelines
As the main purpose of these routes is to serve a certain downtown or urban area, business Interstates are typically routed along surface roads rather than limited-access freeway segments. This allows the business route to directly connect to and navigate a local street network, providing more accessible connections to the central business district. Business Interstates are often designated along existing city streets or arterials that already have a strong commercial and retail presence, rather than cutting through the urban core on a new alignment.

Since business Interstates are primarily routed along surface roads, they do not have to meet the strict design standards required for the mainline Interstate Highway System in order to qualify for that kind of designation. However, despite sharing the "Interstate" designation and similar shield design, business Interstates are not actually considered part of the mainline Interstate Highway System. They are treated more as auxiliary or supplemental routes that complement the overall Interstate network, rather than being fully integrated components.

The design standards for business Interstates are more akin to the guidelines used for new U.S. Highway routes. While they aim to maintain a baseline of safety and continuity, the standards are less stringent than the exacting specifications for lane widths, access control, grade separations, and other factors that define the main Interstate Highway network.

Business route classifications
Business Interstates are signed with green shields that visually resemble the standard Interstate Highway shield, but with a few key differences. The word BUSINESS is used instead of INTERSTATE, and, above the number, where the state name is sometimes included, the word LOOP or SPUR appears.

A business loop has both ends connected to its parent Interstate route. This allows the business loop to provide direct access to the central business district or other major destinations within a city or town. Many business loops were created to replace a decommissioned U.S. Route. One example includes all the I-5 business loops in northern California, which replaced US 99W through towns like Woodland, Arbuckle, or Williams. Sometimes, a business loop may either be cosigned with or supplement an active U.S. Route, such as I-70 Business Loop in Denver, Colorado, that follows US 40 and Colfax Avenue across the metropolitan area.

A business spur has one end connected to the parent Interstate route, while the other end dangles or terminates at a specific destination, often the downtown or central business district of a city or town. One example is Business Spur I-75 into Bay City, Michigan. Sometimes, a business spur originates from an Interstate's terminus and continues into the city/destination. An example of this is I-20 Business Spur into Florence, South Carolina, which originates from I-20's eastern terminus at I-95.

While most business Interstates are usually routed along surface roads, they are sometimes routed onto freeways. Some of these stretches of freeways were once designated as mainline Interstates themselves, such as I-85 Business Loop in Spartanburg, South Carolina, and I-80 Business Loop in Sacramento, California.

List
Defunct routes are listed in italics.

Interstate 5

 * I-5 Bus.—San Ysidro, National City and San Diego, California
 * I-5 Bus.—San Diego, California
 * I-5 Bus.—Solana Beach, California
 * I-5 Bus.—San Clemente, California
 * I-5 Bus.—Irvine, California
 * I-5 Bus.—Los Angeles, California
 * I-5 Bus.–Coalinga, California
 * I-5 Bus.—Woodland, California
 * I-5 Bus.—Arbuckle, California
 * I-5 Bus.—Williams and Maxwell, California
 * I-5 Bus.—Willows and Orland, California
 * I-5 Bus.—Red Bluff, California
 * I-5 Bus.—Cottonwood, California
 * I-5 Bus.—Anderson and Redding, California
 * I-5 Bus.—Dunsmuir, California
 * I-5 Bus.—Mount Shasta, California
 * I-5 Bus.—Weed, California
 * I-5 Bus.—Yreka, California
 * I-5 Bus.—Vancouver, Washington
 * I-5 Bus.—Castle Rock, Washington
 * I-5 Bus.—Chehalis and Centralia, Washington
 * I-5 Bus.—Olympia, Washington
 * I-5 Bus.—Fife, Washington and Midway (near Des Moines, Washington)
 * I-5 Bus.—Seattle, Washington
 * I-5 Bus.—Marysville, Washington and Everett, Washington
 * I-5 Bus.—Bellingham, Washington

Interstate 205

 * I-205 Bus.—Tracy, California

Interstate 8

 * I-8 Bus.—San Diego, California
 * I-8 Bus.—El Cajon, California
 * I-8 Bus.—Alpine, California
 * I-8 Bus.—El Centro, California
 * State Bus. Route 8 (1)—Winterhaven, California and Yuma, Arizona
 * State Bus. Route 8 (3)—Gila Bend, Arizona

Interstate 10

 * I-10 Bus.—Ontario, California
 * I-10 Bus.—Colton, California
 * I-10 Bus.—Indio, California
 * I-10 Bus.—Blythe, California
 * State Bus. Route 10 (1)—Quartzsite, Arizona
 * State Bus. Route 10—Phoenix, Arizona
 * State Bus. Route 10—Casa Grande, Arizona
 * State Bus. Route 10 (2)—Tucson, Arizona
 * State Bus. Route 10 (3)—Benson, Arizona
 * State Bus. Route 10 Spur—Benson, Arizona
 * State Bus. Route 10 (4)—Willcox, Arizona
 * State Bus. Route 10 (5)—Bowie, Arizona
 * State Bus. Route 10 (6)—San Simon, Arizona
 * BL 21—Lordsburg, New Mexico
 * BL 22—Deming, New Mexico
 * BL—Las Cruces, New Mexico
 * Bus. I-10-C—Sierra Blanca, Texas
 * Bus. I-10-D—Van Horn, Texas
 * Bus. I-10-F—Balmorhea, Texas
 * Bus. I-10-G—Fort Stockton, Texas

Interstate 15

 * I-15 Bus.—Escondido, California
 * I-15 Bus.—Victorville, California
 * I-15 Bus.—Barstow, California
 * I-15 Bus.—Mesquite, Nevada
 * I-15 Bus.- St. George, Utah
 * I-15 Bus.—Cedar City, Utah
 * I-15 Bus.—Parowan, Utah
 * I-15 Bus.—Beaver, Utah
 * I-15 Bus.—Fillmore, Utah
 * I-15 Bus.—Holden, Utah
 * I-15 Bus.—Nephi, Utah
 * I-15 Bus.—Layton, Utah
 * I-15 Bus.—Brigham City, Utah (co-signed with I-84 Bus.)
 * I-15 Bus.—Tremonton, Utah (co-signed with I-84 Bus.)
 * I-15 Bus.—Pocatello, Idaho
 * I-15 Bus.—Idaho Falls, Idaho
 * I-15 Bus.—Butte, Montana
 * I-15 Bus.—Helena, Montana
 * I-15 Bus.—Great Falls, Montana (co-signed with I-90 Bus.)
 * I-15 Bus.—Conrad, Montana
 * I-15 Bus.—Shelby, Montana

Interstate 17

 * State Bus. Route 17—Black Canyon City, Arizona

Interstate 19

 * State Bus. Route 19 (1)—Nogales, Arizona
 * State Bus. Route 19 (2)—Sahuarita, Arizona – Tucson, Arizona (Still shown on all Rand McNally road atlases.)

Interstate 20

 * Bus. I-20-B—Pecos, Barstow, Texas
 * Bus. I-20-D—Monahans, Texas
 * Bus. I-20-E—Odessa, Midland, Texas
 * Bus. I-20-F—Stanton, Texas
 * Bus. I-20-G—Big Spring, Texas
 * Bus. I-20-H—Westbrook, Texas
 * Bus. I-20-J—Colorado City, Texas
 * Bus. I-20-K—Loraine, Texas
 * Bus. I-20-L—Roscoe, Texas
 * Bus. I-20-M—Sweetwater, Texas
 * Bus. I-20-N—Trent, Texas
 * Bus. I-20-P—Merkel, Texas
 * Business I-20-Q—Tye, Texas
 * Bus. I-20-R—Abilene, Texas
 * Bus. I-20-T—Baird, Texas
 * I-20 BS—Florence, South Carolina

Interstate 24

 * I-24 Bus.—Paducah, Kentucky
 * Downtown Loop —Paducah, Kentucky

Interstate 25

 * BL (11)—Williamsburg, New Mexico – Truth or Consequences, New Mexico
 * BL (12)—Socorro, New Mexico
 * BL (13)—Belen, New Mexico
 * BL (14)—Santa Fe, New Mexico
 * BL (15)—Las Vegas, New Mexico
 * BL (16)—Springer, New Mexico
 * BL (17)—Raton, New Mexico
 * State Highway 25A—Trinidad, Colorado
 * State Highway 25B Spur—Aguilar, Colorado
 * State Highway 25C—Walsenburg, Colorado
 * State Highway 25 Bus.—Colorado Springs, Colorado
 * State Highway 25 Bus.—Castle Rock, Colorado (likely unsigned)
 * I-25 Bus.—Cheyenne, Wyoming
 * I-25 Bus.—Chugwater, Wyoming
 * I-25 Bus.—Wheatland, Wyoming
 * I-25 Bus.—Douglas, Wyoming
 * I-25 Bus.—Glenrock, Wyoming
 * I-25 Bus.—Casper, Wyoming
 * I-25 Bus.—Buffalo, Wyoming

Interstate 126

 * I-126 BS—Columbia, South Carolina

Interstate 526

 * I-526 BS—Mount Pleasant, South Carolina

Interstate 27

 * Bus. I-27-T—Hale Center, Texas
 * Bus. I-27-U—Plainview, Texas

Interstate 29

 * I-29 Bus.—Saint Joseph, Missouri
 * I-29 Bus.—Elk Point, South Dakota
 * I-29 Bus.—Brookings, South Dakota
 * I-29 Downtown Spur—Sioux Falls, South Dakota
 * I-29P Bus.—North Sioux City, South Dakota (unsigned)

Interstate 229

 * I-229 Downtown Loop—Sioux Falls, South Dakota

Interstate 30

 * I-30 Bus.—Benton, Arkansas
 * I-30 Bus.—Little Rock, Arkansas

Interstate 35

 * BS I-35-A—Laredo, Texas
 * Bus. I-35-B—Encinal, Texas
 * Bus. I-35-C—Cotulla, Texas
 * Bus. I-35-D—Dilley, Texas
 * Bus. I-35-E—Pearsall, Texas
 * Bus. I-35-H—New Braunfels, Texas
 * Bus. I-35-J—Kyle, Texas
 * Bus. I-35-L—Round Rock, Texas
 * Bus. I-35-M—Georgetown, Texas (Cancelled July 2006)
 * BS I-35-V—Alvarado, Texas
 * Bus. I-35-X—Sanger, Texas
 * I-35 BL—Ames, Iowa
 * I-35 BL—Clear Lake, Iowa
 * I-35 Bus.—Faribault, Minnesota
 * I-35 Bus.—Albert Lea, Minnesota
 * I-35 Bus.—Pine City, Minnesota

Interstate 40

 * I-40 Bus.—Needles, California
 * State Bus. Route 40 (0)—Kingman, Arizona
 * State Bus. Route 40 (1)—Seligman, Arizona
 * State Bus. Route 40 (2)—Ash Fork, Arizona
 * State Bus. Route 40 (3)—Williams, Arizona
 * State Bus. Route 40 (4)—Flagstaff, Arizona
 * State Bus. Route 40 (5)—Flagstaff, Arizona
 * State Bus. Route 40 (6)—Winslow, Arizona
 * State Route 40 Spur—Winslow, Arizona
 * State Bus. Route 40 (7)—Joseph City, Arizona
 * State Bus. Route 40 (8)—Holbrook, Arizona
 * I-40 Bus.—Gallup, New Mexico
 * I-40 Bus.—Grants, New Mexico
 * I-40 Bus.—Albuquerque, New Mexico
 * Bus. Route 40 (34)—Moriarty, New Mexico
 * Bus. Route 40 (35)—Santa Rosa, New Mexico
 * Bus. Route 40 (36)—Tucumcari, New Mexico
 * Bus. I-40-A —Glenrio, Texas
 * Bus. I-40-B—Adrian, Texas
 * Bus. I-40-C—Vega, Texas
 * Bus. I-40-D—Amarillo, Texas
 * Bus. I-40-F—Groom, Texas
 * Bus. I-40-H—McLean, Texas
 * Bus. I-40-J—Shamrock, Texas
 * I-40 Bus.—Erick, Oklahoma
 * I-40 Bus.—Sayre, Oklahoma
 * I-40 Bus.—Elk City, Oklahoma
 * I-40 Bus.—Clinton, Oklahoma
 * I-40 Bus.—Weatherford, Oklahoma
 * I-40 Bus.—El Reno, Oklahoma
 * I-40 Bus.—Henryetta, Oklahoma
 * I-40 Bus.—Sallisaw, Oklahoma
 * I-40 Bus.—Winston-Salem and Greensboro, North Carolina (built as a freeway; Winston-Salem portion removed in February 2020; Greensboro portion, separated by a six-mile gap, removed September 2008)
 * I-40 Bus.—Raleigh, North Carolina (unsigned; built as a freeway; replaced by Interstate 440)

Interstate 44

 * I-44 Bus.—Joplin, Missouri
 * I-44 Bus.—Sarcoxie, Missouri
 * I-44 Bus.—Mount Vernon, Missouri
 * I-44 Bus.—Springfield, Missouri
 * I-44 Bus.—Lebanon, Missouri
 * I-44 Bus.—Waynesville–St. Robert, Missouri
 * I-44 BS—Ft. Leonard Wood, Missouri
 * I-44 Bus.—Rolla, Missouri
 * I-44 Bus.—Pacific, Missouri

Interstate 45

 * Bus. I-45-F—Corsicana, Texas
 * Bus. I-45-G—Ennis, Texas
 * Bus. I-45-H—Palmer, Texas
 * Bus. I-45-J—Ferris, Texas

Interstate 49

 * I-49 Bus.—Neosho, Missouri
 * I-49 Bus.—Joplin, Missouri
 * I-49 Bus.—Nevada, Missouri
 * I-49 Bus.—Butler, Missouri

Interstate 55

 * I-55 Bus.—New Madrid, Missouri
 * I-55 Bus.—Cape Girardeau-Fruitland, Missouri
 * I-55 Bus.—Crystal City, Missouri
 * I-55 Bus.—Springfield, Illinois
 * I-55 Bus.—Lincoln, Illinois
 * I-55 Bus.—Bloomington-Normal, Illinois

Interstate 65

 * I-65 Bus.—Lebanon, Indiana

Interstate 69

 * BL I-69—Charlotte, Michigan
 * BL I-69—Coldwater, Michigan
 * BL I-69—Lansing, Michigan
 * BL I-69—Port Huron, Michigan

Interstate 70

 * I-70 Bus.—Richfield, Utah
 * I-70 BS—Salina, Utah
 * I-70 Bus.—Green River, Utah
 * I-70 Bus.—Grand Junction, Colorado
 * I-70 Bus.—Palisade, Colorado
 * I-70 Bus.—Rifle, Colorado (unsigned)
 * I-70 Bus.—Silt, Colorado (unsigned)
 * I-70 Bus.—Eagle, Colorado (unsigned)
 * I-70 Bus.—Edwards, Colorado (unsigned)
 * I-70 Bus.—Avon, Colorado
 * I-70 Bus.—Frisco, Colorado
 * I-70 Bus.—Idaho Springs, Colorado
 * I-70 Bus.—Denver, Colorado
 * I-70 Bus.—Watkins, Colorado
 * I-70 Bus.—Strasburg, Colorado (unsigned)
 * I-70 Bus.—Deer Trail, Colorado (unsigned)
 * I-70 Bus.—Agate, Colorado (unsigned)
 * I-70 Bus.—Limon, Colorado
 * I-70 Bus.—Vona, Colorado (unsigned)
 * I-70 Bus.—Burlington, Colorado
 * I-70 Bus.—Colby, Kansas
 * I-70 Bus.—Oakley, Kansas
 * I-70 Bus.—Hays, Kansas
 * I-70 Bus.—Boonville, Missouri
 * I-70 Bus.—Columbia, Missouri
 * I-70 Bus.—St. Charles, Missouri
 * I-70 Bus.—Springfield, Ohio

Interstate 72

 * I-72 Bus.—Jacksonville, Illinois

Interstate 75

 * BS I-75—Sault Ste. Marie, Michigan
 * BL I-75—St. Ignace, Michigan
 * BL I-75—Gaylord, Michigan
 * BL I-75—Grayling, Michigan
 * BL I-75—Roscommon, Michigan
 * BL I-75—West Branch, Michigan
 * BL I-75—Saginaw, Michigan
 * BL I-75—Pontiac, Michigan
 * BL I-75—Findlay, Ohio
 * BL I-75—Sidney, Ohio
 * BL I-75—Troy–Piqua, Ohio
 * I-75 Bus.—Cordele, Georgia
 * I-75 Bus.—Adel, Georgia
 * I-75 Bus.—Tifton, Georgia
 * I-75 Bus.—Valdosta, Georgia

Interstate 375

 * BS I-375—Detroit, Michigan (unsigned)

Interstate 76 (west)

 * State Highway 76B—Keenesburg, Colorado (unsigned)
 * I-76 Bus.—Fort Morgan, Colorado—Sterling, Colorado

Interstate 376

 * I-376 Bus.—Moon Township, Pennsylvania (created in 2009, replacing PA 60 Bus.. )

Interstate 80

 * I-80 Bus.—Sacramento, California (built as a freeway; western segment unsigned since 2016)
 * I-80 BS—Sacramento, California
 * I-80 Bus.—Truckee, California
 * I-80 Bus.—Lincoln, Nebraska
 * I-80 Bus.—Sidney, Nebraska
 * I-80 Bus.—Verdi, Nevada
 * I-80 Bus.—Reno–Sparks, Nevada
 * I-80 Bus.—Winnemucca, Nevada
 * I-80 Bus.—Carlin, Nevada
 * I-80 Bus.—Battle Mountain, Nevada
 * I-80 Bus.—West Wendover, Nevada and Wendover, Utah
 * I-80 Bus.—Evanston, Wyoming
 * I-80 Bus.—Fort Bridger-Lyman, Wyoming
 * I-80 Bus.—Green River, Wyoming
 * I-80 Bus.—Rock Springs, Wyoming
 * I-80 Bus.—Rawlins, Wyoming
 * I-80 Bus.—Laramie, Wyoming
 * I-80 Bus.—Cheyenne, Wyoming
 * I-80 Bus.—Pine Bluffs, Wyoming

Interstate 83

 * I-83 Bus.—York, Pennsylvania

Interstate 84 (east)

 * I-84 Bus.—Newtown, Connecticut (now signed as part of US 6 and Route 25)

Interstate 84 (west)

 * I-84 Bus.—Nampa and Caldwell, Idaho (Part of old US 30)
 * I-84 Bus.—Mountain Home, Idaho
 * I-84 Bus.—Hammett, Idaho
 * I-84 Bus.—Glenns Ferry, Idaho
 * I-84 Bus.—Bliss, Idaho (unsigned)
 * I-84 Bus.—Jerome, Idaho (possibly being planned further)
 * I-84 Bus.—Burley and Heyburn, Idaho
 * I-84 Bus.—Tremonton, Utah (co-signed with I-15 Bus.)
 * I-84 Bus.—Brigham City, Utah (co-signed with I-15 Bus.)

Interstate 85

 * I-85 Business—Greensboro, North Carolina (decommissioned in 2019, though signage was not fully eliminated until late 2023)
 * I-85 Business—Spartanburg, South Carolina (built as a freeway)

Interstate 385

 * I-385 BS—Greenville, South Carolina (unsigned since 2007)

Interstate 585

 * I-585 BS—Spartanburg, South Carolina

Interstate 86 (west)

 * I-86 Bus.—American Falls, Idaho

Interstate 89

 * I-89 BS—Lebanon, New Hampshire

Interstate 90

 * I-90 Bus.—Ellensburg, Washington
 * I-90 Bus.—Moses Lake, Washington
 * I-90 Bus.—Medical Lake, Washington
 * I-90 Bus.—Spokane Valley, Washington
 * I-90 Bus.—Wallace, Idaho
 * I-90 Bus.—Missoula, Montana
 * I-90 Bus.—Deer Lodge, Montana
 * I-90 Bus.—Butte, Montana (co-signed with I-15 Bus.)
 * I-90 Bus.—Billings, Montana
 * I-90 Bus.—Sheridan, Wyoming
 * I-90 Bus.—Buffalo, Wyoming
 * I-90 Bus.—Gillette, Wyoming
 * I-90 Bus.—Moorcroft, Wyoming
 * I-90 Bus.—Sundance, Wyoming
 * I-90 Bus.—Spearfish, South Dakota
 * I-90 Bus.—Sturgis, South Dakota
 * I-90 Bus.—Rapid City, South Dakota
 * I-90 Bus.—Wall, South Dakota
 * I-90 Bus.—Kadoka, South Dakota
 * I-90 BS—Belvidere, South Dakota
 * I-90 Bus.—Murdo, South Dakota
 * I-90 Bus.—Vivian, South Dakota
 * I-90 Bus.—Presho, South Dakota
 * I-90 Bus.—Oacoma–Chamberlain, South Dakota
 * I-90 BS—White Lake, South Dakota (unsigned)
 * I-90 Bus.—Plankinton, South Dakota
 * I-90 Bus.—Mitchell, South Dakota
 * I-90 BS—Sioux Falls, South Dakota

Interstate 94

 * BL I-94—Benton Harbor–St. Joseph, Michigan
 * BS I-94—Kalamazoo, Michigan
 * BL I-94—Battle Creek, Michigan
 * BL I-94—Marshall, Michigan
 * BL I-94—Albion, Michigan
 * BL I-94—Jackson, Michigan
 * BL I-94—Ann Arbor, Michigan
 * BL I-94—Port Huron, Michigan

Interstate 95

 * I-95 Bus.—Brunswick, Georgia
 * I-95 Bus.—Darien, Georgia
 * I-95 Bus.—Fayetteville, North Carolina
 * I-95 Bus.—Wilson and Rocky Mount, North Carolina
 * I-95 Bus.—Emporia, Virginia
 * I-95 Bus.—Wilmington, Delaware (proposed around 2000, I-95 would have shifted to what is still I-495,, but rejected by city's mayor—section was temporarily signed as I-895 in early 1980s.)
 * I-95 Bus.- Mystic, Connecticut

Interstate 495

 * I-495 BS—Lowell, Massachusetts (built as a freeway)

Interstate 96

 * BS I-96—Muskegon, Michigan
 * BS I-96—Portland, Michigan
 * BL I-96—Lansing, Michigan
 * BL I-96—Howell, Michigan
 * BL I-96—Farmington, Michigan
 * BS I-96—Detroit, Michigan

Interstate 196

 * BL I-196—South Haven, Michigan
 * BL I-196—Holland, Michigan
 * BS I-196—Wyoming, Michigan

Interstate 496

 * Capitol Loop—Lansing, Michigan

Interstate 696

 * BS I-696—Detroit, Michigan (built as a freeway)