Co-ops first arose in the city in the 1920s. Building slowed during the Great Depression, but their numbers expanded after World War II. Conversions also expanded during the postwar years and several local architects became well known for their co-op designs. The model thrived and has become a vital part of the city's fabric. Local historian Steve McKevitt tells the stories of each existing District co-op, using both historic and modern images to detail their development and architecture.