This expansion of the slave state of Missouri was in violation of the Missouri Compromise of 1820, which prohibited the extension of slavery in the former Louisiana Territory north of the parallel 36°30′ north except within the boundaries of the state of Missouri as defined at the time of the adoption of the Missouri Compromise. The area acquired was almost as large as the states of Delaware and Rhode Island combined, and extended Missouri westward along the river. St. Joseph, one of the main ports of departure for the westward migration of American pioneers, was located in the new acquisition.