However, when the Mexican–American War began in 1846, Buffum was forced to leave his post and move to California with his regiment.
He arrived in San Francisco Bay as the lieutenant of the 1st Regiment of New York Volunteers.
After his discharge from the army in 1848, he decided to remain in California and try his hand at panning gold.
These specific experiences were recorded in his book Six Months in the Gold Mine, published in 1850.
He was very well respected in his community and was elected to the California State Assembly, serving in the session of 1855.