Answer:
The discover gold in California
Step-by-step explanation:
The discovery of gold in California helped to speed development of the western United States.
Soon after the Civil War ended in eighteen sixty-five, thousands of Americans began to move west to settle the land.
People in the U.S. moved steadily west through all of U.S. history. The first settlements founded by Europeans were on the east coast. ... The Gold Rush is an exception - they were seeking gold - but the westward settlement prior to the war and after the war had the intention of securing land on which to farm or ranch.
Some other reasons are
The opportunity to work in the cattle industry; to be a “cowboy”
Faster travel to the West by railroad; availability of supplies due to the railroad.
The opportunity to own land cheaply under the Homestead Act.