|“||It's not a mental institution. Think of it as more like...a spa. People call it the Canyon Ranch of Delaware.||”|
— Isabel Randall
The Preserve at Addison-Stevens is a clinic for troubled patients in Delaware. Courtney DiLaurentis was supposed to transfer from The Radley to The Preserve in the early fall of sixth grade, but her twin Alison was sent instead. Hanna Marin spent a brief amount of time at the clinic in her junior year of high school. Later, Kelsey is sent to the preserve after she is saved by Emily from committing suicide at Floating Man's Quarry.
The Preserve is located close to the Delaware-Pennsylvania border and is touted as a luxury clinic. It serves a wide variety of people and it has a ward exclusively for young patients. When the Radley was closed, Courtney DiLaurentis was scheduled to move to the Preserve on a Saturday morning in late September. However, she managed to fool her mother Jessica into believing she was Alison. As a result, the real Ali was taken to the Preserve. She stayed at the clinic from sixth grade to her junior year of high school.
Hanna's dad Tom sent her to the Preserve after she, Spencer, Aria, and Emily claimed to see Ali while escaping from a fire in Spencer's neighborhood. She quickly befriended an anorexic girl named Iris and teased the less popular girls in their ward. However, Hanna's friendship with Iris is soon ruined. The brunette later discovers a drawing of Ali's face in Iris' secret hideout and tries to get answers from her, but the blonde only taunts her.
In "Wanted" the truth about the DiLaurentis twins is revealed and Ali blames the Pretty Little Liars for her stint in the Preserve. Iris knew everything about Ali's plan to get revenge on the girls and she even knew that Hanna would be her roommate. Melissa Hastings was the first to uncover the truth about Ali after visiting Iris at the Preserve, but she was knocked unconscious and kidnapped by Alison shortly after leaving the facility.
- According to Ruthless, the full name of the clinic is The Preserve at Addison-Stevens Mental Wellness And Rehab
- The Preserve is described by Hanna as "more like a railroad baron's mansion than a hospital", with Grecian columns, bronze statues, topiaries, and several terraces on the upper floors. The clinic also has an extensive spa facility.
- Phones, Internet access, newspapers, magazines, and TV are not allowed at the Preserve. However, patients do have access to DVDs, books, and board games.
- Iris has been in and out of the Preserve since she was 11–12 years old. She has had a long struggle with anorexia but she's not inclined to truly get better.
- As the self-appointed queen bee of the Preserve, Iris has several connections that she takes advantage of. She has access to a small lounge that only a few staff members know about and she also has a staff member sneak in gossip magazines like People and US Weekly.
- The walls of the secret lounge are covered with drawings from the patients who managed to gain access to the room over the years. One of these drawings is of Alison DiLaurentis. Next to the drawing is Courtney's name with a winking smiley face.
- When she was 13, Iris returned home in June around the same time Courtney was killed by Alison. However, she was put back in the Preserve in October of that same year after her weight dropped.
- Tabitha Clark had also spent some time at the Preserve; according to Graham, it was for depression and family problems.
- Nick Maxwell spent several years there as well
- It costs one thousand dollars a day to stay at the Preserve
- Every patient has a private tutor