Furthermore, they were seldom solidly constructed stockades with numerous permanent buildings. Sometimes, they were little more than a couple of blockhouses. Other types of fortifications were constructed by traders to protect their businesses and by settlers to protect their homes.

As more and more settlers moved west in the 19^th century Army posts were established on the basis of anticipated use, sometimes to keep the Indian tribes from waging war with each other and at other times, to keep white settlers from encroaching upon native lands.

It was generally only when white settlers insisted on encroaching upon native lands, especially during the many gold and silver rushes, that the Indians retaliated. Only then did the forts’ primary purpose change to protecting the settlers. As westward expansion continued, threatening the Indian's livelihood, war between the whites and Indians intensified, resulting in the push of Native Americans onto reservations. Once the Indians were placed on reservations, some forts served as Indian agencies and distribution points for annuities given to tribes under treaty agreements.

When the many trails began to open such, as the Santa Fe Trail in the 1820’s and the Oregon Trail in the 1840’s, traders and pioneers often met with not only, opposition from the tribes, but also, by road agents interested in relieving them of their money or their goods. In response, more forts were established to protect commerce along the trails.

When establishing a new fort, the soldiers would sometimes occupy buildings already established, but more often, were required to construct the new fort from materials available in the area. In forested areas, wood was usually used; adobe in the desert, and stone, where available. The typical frontier fort consisted of officers' quarters, barracks, stables, storehouses, and headquarters buildings, grouped around a central parade ground. Most forts did not have walls surrounding them because attacks were generally unlikely.

Many army posts were referred to as “camps,” when there were only a few people assigned to the location or when the site was temporary. To be considered a “fort,” a full contingent of troops had to be permanently assigned to it. Both forts and camps were utilized by the U.S. Army during the Frontier Campaigns.