Final answer:
Edward L. Doheny and Charles A. Canfield were the first to discover LA's rich oil deposits, leading to the city's oil boom in the late 19th century.
Step-by-step explanation:
The first discovery of LA's rich oil deposits was made by Edward L. Doheny in 1892. Doheny and his partner Charles A. Canfield drilled the first successful oil well in Los Angeles, which marked the beginning of the city's oil boom. The oil deposits found in LA were some of the richest in the world at the time, leading to significant economic growth and development in the region.