In the years that followed, the Rockies were gradually explored, treaties were signed and broken with resident tribes, and people with widely differing goals entered the San Luis Valley from the United States and Mexico. In 1852, Fort Massachusetts was built and then relocated to Fort Garland, about southeast of the Great Sand Dunes, to safeguard travel for settlers following the explorers into the valley. Although many settlers arrived via the trails from Santa Fe or La Veta Pass, several routes over the Sangre de Cristos into the valley were well-known to American Indians and increasingly used by settlers in the late 1800s. Medano Pass, also known as Sand Hill Pass, and Mosca Pass, also called Robidoux's Pass, offered more direct routes from the growing front range cities and dropped into the valley just east of the Great Sand Dunes. Trails were improved into wagon routes and eventually into rough roads. The Mosca Pass Toll Road was developed in the 1870s, and stages and the mail route used it regularly through about 1911 when the western portion was damaged in a flash flood. Partially rebuilt at times in the 1930s through the 1950s, the road was repeatedly closed due to flood damage and is now a hiking trail.