There does not seem to be very much information availabe about the Belmont Speedway.
It was in the area of where the PG&E complex is now located on Industrial Road in Belmont. Right across the street from this cache.
A Mr. Ted L. Smith built the racing oval which had its ground breaking on 23 May 1947.
Three months later on 27 July 1947 the first race was held. Some 3,300 people paid to see midget racing on the track's first night of operation. Pictured below is the Belmont Speedway
Another earlier speedway ... The San Carlos Speedway ... was built in 1921 from lumber and hosted only four races before it burned to the ground on June 18, 1922.
This speedway was also referred at times as the San Francisco Speedway but was always located in San Carlos.
The mile and a quarter oval track was adjacent to the San Carlos Aviation Field. The Field hanger was just off one of Speedway's 38 degree banked turns. The new track was named the Greater San Francisco Speedway. The cost of the project is unknown, but Prince and Pillsbury are said to have spent a quarter million dollars building the Beverly Hills track. That was a considerable amount in the early 1920s. The championship motorcycle races came to San Carlos on May 14, 1922. Ralph Hepburn was already having a successful season on his Indian Power Plus Daytona racer, and that did not change at San Carlos. He dominated the days races, winning two, and finishing third in another. Hepburn set a blistering pace of over 100 miles per hour, to win the 50 Mile Championship Race. He also picked up the Barney Oldfield Diamond Medal for his win.