Wikipedia:WikiProject U.S. Roads/Pennsylvania/All-time list

Given are the years of the first and last official maps the routes appear on. Unfortunately only one map per decade is available. Other official maps: 1925 (key), 1926 (key), 1926 (partial), 1927 (key), 1927 (partial - note the widespread system that was completely changed by 1928), 1928, 1929, 1930, 1933, 1927.