Dr. Rowland Willard was the first U.S. physician to travel the entire distance of the Santa Fe Trail from Saint Charles, Missouri, to Chihuahua, Mexico. His diaries and autobiography provide a written record of his wilderness journeys over the Santa Fe Trail and down the Chihuahua Trail portion of El Camino Real. His pocket diaries chronicle his daily experiences on a wilderness journey from his home in Saint Charles, Missouri, beginning in May 1825. Sometime after he retired in 1867, Dr. Willard penned a descriptive autobiography that expanded on his diary entries—writings that were hurriedly written while en route or later during brief lulls in his daily practice.