In 2007, Southland and the 1/18th Cavalry, 40th Infantry Div. vacated the armory in Pomona and Southland for the next two years operated under a joint operational agreement with Squadron 20 of the Civil Air Patrol.
Southland returned to the Pomona Armory in 2009 and conducted drills at the Park address and later the National Guard Armory on 1st Street. For the next 10 years, Southland called the Armory home.
In January 2020, Southland Young Marines moved to Pomona Presbyterian Church, 401 N. Gibbs Street, Pomona, CA.
The Southland Unit was formed in 2000, from it's sister unit, Inland Valley Young Marines in San Bernardino.
Southland graduated its first recruit class at the Ontario National Guard Armory in 2001, and shortly after moved command to the City of Pomona's National Guard Armory on Park Ave.