From 1871-1879, Lieutenant George M. Wheeler (1842-1905), army engineer and surveyor, led a series of geographical surveys with the purpose of mapping the land west of the 100th Meridian through much of California, Nevada, present-day Arizona, New Mexico, and Colorado. Timothy H. O’Sullivan (1840-1882) and William Bell (1839-1915) were the primary photographers who traveled on the surveys from 1871-1873 documenting the geological features of the American West. This photograph taken by O'Sullivan in 1871 shows the junction of the Diamond and Colorado Rivers in the Grand Cañon (today known as Grand Canyon National Park in Arizona). A single figure stands on the rocks in the foreground where the rivers meet as the canyon walls rise up in the background. The original negative number, 142, is written on the right-hand image, likely by the photographer.