"This was our home. My mother and my grandmother found this place for the group. There were so many of us then. Men and women... kids. My mom and I built a garden. Me and my brother used to play right here. But then the Saviors came. And Simon wanted what we had. He gave us our final warning. Afterward, we ran. And we tried to forget."
—Cyndie explains Oceanside's history with the facility to Maggie and Daryl.[src]
Nothing is known about the facility prior to the outbreak though the name suggests that it was once used for recovery purposes, likely drug or alcohol.
After the outbreak began, the facility was discovered by Natania and her daughter and transformed into a safe-zone for their group of survivors. Many survivors lived there, men, women, and children. However, a group of bandits eventually came, led by Simon. Rather than giving in to the their demands, the survivors resisted, but ultimately lost. In retaliation, Simon had every male survivor over the age of ten executed and the words "Final Warning" painted on the side of the building in spite of any and all pleas for mercy. In the aftermath, those who remained, reduced to women and children under the age of ten, fled and found a new home.
Following the war with the Saviors and the execution of Gregory, the remaining survivors, now known as Oceanside, decided to exact revenge upon the surviving Saviors who had taken part in the massacre. One by one, Oceanside kidnapped and brought the Saviors back to Hallowbrant and executed them on the same location that their people had died on. In particular, Beatrice killed Justin for murdering her husband. However, Beatrice killed Justin with her spear gun through the chest and failed to put him down before he could turn. As a result, after being fed on by a herd, Justin reanimated and was eventually found by Maggie and Kal, exposing the executions.
During the investigation into the murders, Arat, the last of the Saviors from the massacre, was kidnapped. After finding one of Beatrice's spears, Daryl realized who the killers were and Maggie led him to the facility which she had found some time prior and deduced was Oceanside's former home. Maggie and Daryl arrived as Oceanside was preparing to execute Arat for her crimes, in particular the murder of Cyndie's younger brother. After Cyndie forced Arat to admit to saying "no exceptions" after making Cyndie beg for her brother's life, Daryl and Maggie were reminded of Glenn's death at Negan's hands and walked away. As they left, Cyndie killed Arat with a spear to the back of the head for murdering her little brother.
Though never seen until "Warning Signs", it was mentioned several times in relation to the Oceanside massacre.
The name of the facility, seen on the wall near where the biofuel is found, appears to be partially burnt, likely in the battle with the Saviors.
It is unknown exactly how many Saviors were involved in the massacre, but it was at least 9: six unnamed Saviors, Justin, Arat and Simon. There were likely more who died in the war with the Militia as Simon did.