Zebulon Pike was the first American to explore the San Luis Valley. In the dead of winter, Pike decided to take ten men to cross the Sangre de Cristos in search of Red River. They crossed the Wet Mountain in deep snow. Because three of their party was suffering from exhaustion, they were left in a temporary shelter. The others crossed Medano Pass and saw the Great Sand Dunes. On July 31, 1807, Pike raised the U. S. flag over the fort they had built on the Conejos River. This was the first time the flag was flown in the Rocky Mountain region. The site of the stockade was purchased by the state in 1924 and in 1952 a log fort was erected, which can be visited today.

Before any permanent settlements were established in the San Luis Valley, Mexico ceded all of the Southwest to the United States as a result of the Mexican War of 1846. The Utes did not recognize the United States newly acquired control of the Valley and disrupted early settlements. The government recognized that if the fledgling Mexican settlements were to survive, a military presence was essential.

Fort Massachusetts was quickly rendered ineffective and was abandoned; today only ruins remain at its site. The forts consolidated and solidified the new government’s expansionist ideas. Unlike Spain and Mexico, the U.S. was intent on realizing its “Manifest Destiny” and would use a military presence to ensure that its newly acquired land was settled properly.

Zebulon Pike was the first American to explore the San Luis Valley. In the dead of winter, Pike decided to take ten men to cross the Sangre de Cristos in search of Red River. They crossed the Wet Mountain in deep snow. Because three of their party was suffering from exhaustion, they were left in a temporary shelter. The others crossed Medano Pass and saw the Great Sand Dunes. On July 31, 1807, Pike raised the U. S. flag over the fort they had built on the Conejos River. This was the first time the flag was flown in the Rocky Mountain region. The site of the stockade was purchased by the state in 1924 and in 1952 a log fort was erected, which can be visited today.