In 1806 and 1807, a U.S. Army expedition led by Lt. Zebulon M. Pike explored the United States' new southwestern boundary with New Spain. The party included Dr. John H. Robinson, Sgt. William Meek, Corp. Jeremish Jackson, and privates John Brown, Jacob Carter, William Gordon, Theodore Miller, John Mountjoy, Alexander Roy, and Freegift Stout. Pike's journal recorded the hardships of the journey across the plains and toward the Rio del Norte, including severe winter conditions, inadequate clothing and blankets, and a hard march that brought the men to the river on January 30, 1807. The route passed through a landscape long traveled by humans for centuries, beneath mountains encircling Mount Blanca, known to the Navajo as the Sacred Mtn. of the East, and near destinations now called the Great Sand Dunes and San Luis Lakes. Along with the records of explorers such as Lewis and Clark, Pike's careful logbooks helped mapmakers in Washington create new images of the largely unknown Rocky Mountains, and an original map of this region was published in 1807.