Although the fort was referred to initially as simply the 'Post on the Missouri' it appears soon to have been given, quite appropriately, the name of the governor who planned it and given it its legal birth: i.e. Cavagnial, sometimes incorrectly spelled Cavagnal, and more recently Cavagnolle, although the governor himself signed his name 'Cavagnial'. It appears that the first commandant of the fort was Chevalier Francois Coulon de Villiers.