Before being designated Secondary State Highway 1G (SSH 1G) in 1937, the current roadway that is now SR 538 was a county road through farmland for 26 years. SSH 1G traveled between (PSH 1), also known as US 99, and until 1964, when the current designation of SR 538 was created. US 99 was bypassed by I-5 after 1966 and became Riverside Drive. The roundabout at SR 9 was constructed in 2007 while the Riverside Drive intersection was widened in 2009.