Colt sold his revolver to the Texas Rangers on January 4, 1847:
By the mid-1840s, Colt produced a refinement of his original design in the hopes of attracting capital. No one was willing to take the plunge with him again. He pulled together enough money to have a prototype built, then turned it over to the US War Department (the previous name for the Department of Defense) believing it would earn him a government contract.
On January 4, 1847, Colt received an order from a government agency, but not the one he petitioned. Captain Samuel Walker, a Texas Ranger who used early models of the Colt Paterson in the Seminole Wars in Florida, showed up at Colt’s shop in New York City and asked for 1,000 pistols. Requesting a handful of alterations — a higher caliber, a sixth chamber, faster reload times — Walker provided Colt with the inspiration for the revolver that would make him famous.
Petticoats & Pistols: The 1847 Colt Walker Revolver--As Long As Your Forearm