The Southern California Rapid Transit District was a public transportation agency established in 1964 to serve the Greater Los Angeles area. It was the successor to the original Los Angeles Metropolitan Transit Authority (MTA). California State Senator Thomas M. Rees sponsored the bill that created the RTD, which was meant to correct some deficiencies of the LAMTA, and took over all of the bus service operated by MTA on November 5, 1964. RTD was merged into the Los Angeles County Metropolitan Transportation Authority in 1993.

The Los Angeles Metropolitan Transit Authority was a public agency formed in 1951. Originally tasked with planning for rapid transit in Los Angeles, California, the agency would come to operate the vestiges of defunct private transit companies in the city.