Vrain (May 5, 1802 – October 28, 1870), was the American son of a French aristocrat who immigrated to the United States in the late 18th century; his mother was from St.
Louis, where he was born.
To gain the ability to trade, in 1831 he became a naturalized Mexican citizen in what is now the state of New Mexico.
He formed a partnership with American traders William, George and Charles Bent; together they established the trading post of Bent's Fort.
It was the only privately held fort in the West.
In addition to his trading post business, St.
Vrain formed a business partnership with Cornelio Vigil.
In 1843 the two men petitioned for and received a land grant of approximately 4 million acres located in what is now southeastern Colorado.
However, their plans for development of the area were halted due to the onset of the Mexican–American War, by which the United States acquired the Southwest and California.
Following the creation of the U.S.
provisional government of New Mexico in 1847, St.
Vrain organized a group of volunteers who fought alongside the US Army during the Taos Revolt.
After the deaths of Charles and George Bent, William Bent and St.
Vrain dissolved their partnership.
St.
Vrain settled in Mora, New Mexico Territory.
There he owned saw and flourmills and was a supplier to the U.S.