Originally established as the St. Isidore Catholic Parish in 1921, today the building and site is known as the St. Isidore Historical Plaza — a community center which promotes local California heritage and culture by providing a gathering place for community events and services.

Although much of the original building was destroyed in the Long Beach earthquake in 1933, parishioners rebuilt St. Isidore to its present Spanish Revival architecture style that stands today. In 1999, after the final closing of St. Isidore by the Orange Diocese, a committee of dedicated parishioners and community members formed a non-profit organization to purchase, preserve and protect the St. Isidore site for present and future generations, renaming it the St. Isidore Historical Plaza.

The Los Alamitos Museum Association on November 29, 2011, designated the chapel building at St. Isidore Historical Plaza as the oldest remaining community building in Los Alamitos.