President James Monroe recommended the creation of a series of military posts along the upper reaches of the Mississippi. The objective was to expand contact with the Indians, exploit trade with British companies, and offer protection for settlers. In 1819 exploration began along the Upper Missouri and eventually the string of military posts was established. The American Fur Company began the first full-scale development of the area, and it was Astor who built Fort Union which became a bastion of traders, travellers, and explorers. As other forts expanded into the Dakotas, Iowa, Minnesota, Montana, and the gateway of the upper Rockies it allowed for more settlers, but it also led to hostilities between the various Indian tribes.