Spanish exploration of the upper Rio Grande del Norte was slight and often accidental. In 1694 Diego de Vargas came nearly as far north as present-day Alamosa while detouring around hostile Pueblos, and in 1779 Juan Bautista de Anza passed within a few miles of here on his way to the Arkansas Valley. In 1807 Lt. Zebulon M. Pike led the first U.S. investigation of the upper Rio Grande, although the river still belonged to Spain; Pike supposedly mistook it for the Red River, though Spanish officials believed he may have done so deliberately to spy, and they hauled his entire party off to a Mexican prison. The later search for a cross-country railroad route brought Anglo explorers toward the remote headwaters of the Rio Grande. In 1848 Lt. John C. Frémont entered the San Juan Mountains about fifty miles northeast of here, but heavy December snows forced his expedition to turn back and killed eleven of its thirty-three members. In 1853 Edward Beale and Gwin Heap led a scouting party backed by private supporters of a central Rockies rail corridor and judged the San Juans eminently fit for rail travel, but later that year Capt. John Gunnison reached the opposite conclusion after an arduous trek over Cochetopa Pass. Gunnison’s findings later ended Colorado’s hopes for a transcontinental railroad and left the southern Wyoming route as the only viable option.