Pretty Little Liars season 1

The first season of Pretty Little Liars, based on the books of the same name by Sara Shepard, premiered on June 8, 2010 and concluded on March 21, 2011 on ABC Family.

The show premiered to 2.47 million viewers and retained a regular audience of 2.5 million viewers during its summer run. The summer finale scored 3.07 million viewers, achieving a series high. The show went on hiatus and returned with its winter premiere on January 3, 2011, with 4.20 million viewers, becoming one of ABC Family's top telecasts to date.

Overview
Set in the fictional town of Rosewood, Pennsylvania, Spencer Hastings, Aria Montgomery, Hanna Marin, Emily Fields, and Alison DiLaurentis' lives are irrevocably changed after their clique leader Alison "Ali" goes missing during a sleepover. The four remaining girls forever believe their secrets are safe for all time, but the absence of one of their leaders makes them drift apart. One year later, the former group of friends are forced to reunite after their once-missing friend is discovered dead, and they begin receiving threatening texts from someone named "A," who utilizes secrets that only their dead friend would know to terrorize them. Knowing that if their secrets are out, it will jeopardize them and their futures, the girls decide to team up and figure out who is behind the mask.

Main

 * Troian Bellisario as Spencer Hastings
 * Ashley Benson as Hanna Marin
 * Holly Marie Combs as Ella Montgomery
 * Lucy Hale as Aria Montgomery
 * Ian Harding as Ezra Fitz
 * Bianca Lawson as Maya St. Germain
 * Laura Leighton as Ashley Marin
 * Chad Lowe as Byron Montgomery
 * Shay Mitchell as Emily Fields
 * Nia Peeples as Pam Fields
 * Sasha Pieterse as Alison DiLaurentis

Recurring

 * Keegan Allen as Toby Cavanaugh
 * Tammin Sursok as Jenna Marshall
 * Janel Parrish as Mona Vanderwaal
 * Torrey DeVitto as Melissa Hastings
 * Ryan Merriman as Ian Thomas
 * Chuck Hittinger as Sean Ackard
 * Tyler Blackburn as Caleb Rivers
 * Brendan Robinson as Lucas Gottesman
 * Brant Daugherty as Noel Kahn
 * Lesley Fera as Veronica Hastings
 * Cody Allen Christian as Mike Montgomery
 * Lindsey Shaw as Paige McCullers
 * Bryce Johnson as Darren Wilden
 * Diego Boneta as Alex Santiago

Guest

 * Julian Morris as Wren Kingston
 * Nolan North as Peter Hastings
 * Jim Titus as Officer Barry Maple
 * Yani Gellman as Garrett Reynolds
 * Eric Steinberg as Wayne Fields
 * Jill Holden as Mrs. Welch
 * Amanda Schull as Meredith Sorenson
 * Carlson Young as Amber Victorino
 * Parker Bagley as Jason DiLaurentis
 * Andrea Parker as Jessica DiLaurentis
 * Roark Critchlow as Tom Marin
 * Tilky Jones as Logan Reed
 * Patrick J. Adams as Hardy
 * Sara Shepard as Ms. Shepard
 * 2AM Club as themselves

Development and production
Originally developed as a television series by book packaging company Alloy Entertainment, the idea was described as "Desperate Housewives for teens." Alloy met with author Shepard, and gave her the property to develop into a book series. With Alloy and Warner Horizon interested in producing a Pretty Little Liars television series for years, it was first planned for The WB in 2005 with a different writer. The first novel was published by HarperTeen in October 2006. In June 2008, Alloy noted that it was developing a Pretty Little Liars television pilot for ABC Family. The novels are being adapted for television by I. Marlene King. The series' pilot was filmed in Vancouver in December 2008. Filming for the series moved to Los Angeles from the second episode onward.

Casting
ABC Family began casting for a Pretty Little Liars television pilot in October 2009. Lucy Hale was cast as Aria Montgomery in the project, followed by Troian Bellisario and Ian Harding (as Spencer Hastings and Ezra Fitz, respectively) in November 2009. In December 2009 The Futon Critic confirmed the casting of Ashley Benson as Hanna Marin and Shay Mitchell as Emily Fields, as well as the addition of Laura Leighton as Ashley Marin, Alexis Denisof as Byron Montgomery, Bianca Lawson as Maya, as well as Jean Louisa Kelly and Nia Peeples. The Hollywood Reporter also noted that Torrey DeVitto and Sasha Pieterse landed recurring roles in the pilot.

The Alloy website later confirmed that Pieterse would be playing Alison DiLaurentis and DeVitto would be Melissa Hastings, also noting Janel Parrish as Mona Vanderwaal and Cody Allen Christian, as Mike Montgomery. In April 2010, Chad Lowe replaced Alexis Denisof as Aria's father, Byron Montgomery. Also in April, Holly Marie Combs was cast as Ella Montgomery.