Negotiations to acquire the Louisiana territory, which stretched from New Orleans to Montana’s Canadian border, went back and forth for three years. Finally, an agreement was reached to purchase the territory and the U.S. and France signed the treaty on April 30, 1803. The U.S. Senate ratified it in October.
The actual transfer took place in The Cabildo, then the colonial government building and now a museum along Jackson Square. A formal ceremony changing in land ownership was held in St. Louis in March of 1804.