The California Trail was an emigrant trail of about 1,600 mi (2,600 km) across the western half of the North American continent from Missouri River towns to what is now the state of California. After it was established, the first half of the California Trail followed the same corridor of networked river valley trails as the Oregon Trail and the Mormon Trail, namely the valleys of the Platte, North Platte, and Sweetwater rivers to Wyoming. The trail has several splits and cutoffs for alternative routes around major landforms and to different destinations, with a combined length of over 5,000 mi (8,000 km).

California is a state in the Western United States, lying on the American Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and the Mexican state of Baja California to the south. With over 38.9 million residents across a total area of approximately 163,696 square miles (423,970 km2), it is the most populous U.S. state, the third-largest U.S. state by area, and the most populated subnational entity in North America.