Grayson was born August 20, 1819, in the northwest corner of Louisiana, on the Ouachita River, where his father had a cotton plantation.

[1] After his father died, Mr. Grayson used his inherited funds to invest in a small store.

After meeting frontiersmen in his college years, he developed an insatiable urge to move west.

At Fort Bridging, a conman, L. W. Hastings, persuaded one of the groups to take a shortcut through a mountain pass.

Once Grayson settled in San Francisco, he instantly joined a military group led by Mariano Guadalupe Vallejo.