Charles Stillman, son of Francis and Harriet (Robbins) Stillman, was born at Wethersfield, Connecticut, on November 4, 1810. In February 1828 he went by way of New Orleans to Matamoros. In Mexico he developed a network of mercantile and industrial enterprises, including cotton brokerage and real estate firms, silver mines in Nuevo León and Tamaulipas, merchandise outlets, a shipping company that carried passengers and goods from the Gulf Coast up the river as far as Rio Grande City, and an off-loading, warehousing, and transportation company that carried goods to the Mexican interior as far as Guadalajara. Stillman and his partner, José Morell, established retailing outlets and founded one of the first textile factories at Monterrey. Stillman's Vallecillo mines, between Laredo and Monterrey, produced more than $4 million in silver and lead during the 1850s, and he sold their stock on the New York Stock Exchange.
During the Mexican War Richard King and Mifflin Kenedy joined Stillman in the transport company hauling American troops up the river and supplying them. In the aftermath of the Mexican defeat Stillman purchased massive properties of the Garza grant north and northwest of Matamoros from the children of the first wife of José Narciso Cavazos. The sellers, however, had no legal right to make such a sale, since their father had remarried and the heirs of his second wife, led by the eldest son, Juan N. Cortina, inherited the land from their father upon his death. The excluded children of the first wife "sold" not only the family estates but also the ejido or community property of Matamoros, which was inalienable under Spanish and Mexican law. Nevertheless, Stillman started a town company to sell lots for as much as $1,500 each and named the place Brownsville. By 1850 a population of between 3,000 and 4,000 had concentrated there. Stillman later sold the enormous ranch property north of Brownsville to his partner Kenedy. The lands to the west of Brownsville were left to his son, James Stillman. As a result of land transactions and rising violence, many of the Mexicans fled south of the river and, led by Cortina, carried out a range war that continued for twenty-six years. In 1851 Stillman helped bankroll the attempted invasion of Mexico by José María Carbajal for the purpose of setting up the Republic of the Sierra Madre, which was to extend from Matamoros and Tampico inland to Monterrey, Saltillo, and Nuevo Laredo.
Between 1862 and 1865 Stillman, King, and Kenedy transported Confederate cotton to Matamoros under contract for payment in gold. Stillman bought much of the cotton and sent it to his textile complex at Monterrey, but he sold even more of it in New York through his mercantile firm, Smith and Dunning. The United States government was a major purchaser. On one sale at Manhattan Stillman netted $18,851 on a gross of $21,504. His cotton buyers in Texas included George W. Brackenridge, and one of his major suppliers was Thomas William House. By the end of the war Stillman was one of the richest men in America. He concentrated his investments in the National City Bank of New York, which his son James later controlled, and supplied Brackenridge with $200,000 in the 1870s in order to establish the San Antonio National Bank. Stillman married Elizabeth Pamela Goodrich of Wethersfield, Connecticut, on August 17, 1849. He built a notable home in Brownsville in 1850 and lived in Brownsville and New York City until 1866, when he moved permanently to New York. He died there in December 1875.