I have a section on my page devoted to the Agua Caliente Racetrack:
http://www.antiquegamblingchips.com/AguaaaaaaaTest.htm#horse

Agua Caliente Race Track. "The $2.5 million Agua Caliente racetrack opened in December 1929, one year after the Hotel-Casino opened. It was the site of several industry firsts, including starting gates, safety helmets, photo finishes and “pick six” wagering. Both Phar Lap and Seabiscuit ran and won the Agua Caliente Handicap, which for a time was the richest in North America. The race attracted wealthy Southern Californians. But in 1935, then Mexican President Lázaro Cárdenas outlawed gambling and the resort was closed. Though the race track continued to operate, gambling was not legalized until 1938. In 1971 the original structure of the racetrack was destroyed in a fire. It was later repaired, [reopened for horse racing, struggled for years, eventually discontinued horse racing], and continues operation today as a dog track," Wikipedia.

. 1955 press photo of rare TRIPLE DEAD HEAT, at Agua Caliente track. Since photo finish cameras were introduced in 1934, there have been only two triple dead heats: at the Aqueduct track in New York in 1944, and one here, as of 1955 anyway!

Two great YouTube videos: (1) Phar Lap's thrilling (and last) race at Agua Caliente, and (2) musical excerpts from Dolores del Rio's "In Caliente.":
http://inoldlasvegas.com/agua_caliente.html

Robert