Summerland used to be a horse ranch until Oliver Bird inherited it in the 40's. With Cary Loudermilk's help, Oliver converted it into a facility to shelter mutants. Upon Summerland's completion, Oliver and Cary began their pursuit for more mutants like themselves to fill the facility. Unfortunately, it was during this time that they encountered a mutant named Walter, who sought only to destroy everything they built and stood for. Walter then joined a Division 3, a government organization and nemesis of Summerland. 
Since then, Summerland has fallen under the leadership of Oliver's wife, Melanie Bird. Although, Oliver had been trapped in the Astral Plane for twenty years, his presence within the community never ceased to be felt as his voice could be heard on the espresso machine and in the elevator. Under Melanie's leadership, Summerland has rescued numerous mutants from Division 3 and trained them to control their abilities.
Recruiting David Haller
Summerland came to the aid of David Haller after they sensed him unleashing his power at Clockworks Psychiatric Hospital. Melanie, Kerry, and Ptonomy arrived at Clockworks after the psychic incident took place, and rescued who they thought to be David. However, it was revealed that the mutant they actually rescued was Sydney Barrett, who switched bodies with David earlier and was responsible for causing the psychic incident while she was inhabiting his body. They discovered this after the switch wore off as Sydney reverted to her true form whilst driving with Melanie, Kerry, and Ptonomy. 
Like all the other mutants at Summerland, Sydney underwent talk work with Melanie and memory work with Ptonomy.  The Summerland team also worked on finding David, but he was captured by Division 3 as Kerry and Ptonomy came close to locating him. However, using Ptonomy's ability to manipulate memories, Sydney was able to project herself into David's memory of the day that he was captured by Division 3. She told him that a rescue team was coming for him, and instructed him to slide under the water of the pool that Division 3 was holding him captive in. 
As David complied with Sydney's instructions, an explosion went off that killed all of the Division 3 agents present, with the exception of Clark the Interrogator. Sydney, Kerry, and Ptonomy escaped the facility with David, aided by telekinetic Rudy as they faced off against Division 3 soldiers. They managed to safely make it to a beach, where Melanie was awaiting the team and to meet David. 
Alliance with Division 3
After the Shadow King escaped in Oliver's body, Summerland merged with Division 3 in a truce to find and stop dangerous mutants. The Summerland mutants were also able to convince Division 3 that most mutants are harmless and only wish to live their lives in peace. 
† denotes deceased:
- While Summerland does not appear in any of the Marvel Comics, it identically serves the same purpose of Xavier's School for Gifted Youngsters.