The special issue of Rocky Mountain Geology on Proterozoic magmatism of the Rocky Mountains and environs is in two parts: the first was published in fall 1999, and this second part is the first issue of 2000. Whether or not these parts truly span a change in millennia, the turnover from 1999 to 2000 provides an opportunity for reflection on the changes in geological thinking that have taken place in the years since the first geologic descriptions of the Rocky Mountain region. Systematic geologic descriptions of the Rocky Mountains region began following the Civil War, when national geographical and geological surveys were conducted under the auspices of the War Department and Department of the Interior. Several of these included descriptions of Precambrian rocks, in particular the U.S. Geological Survey of the Territories under F. V. Hayden, the United States Geological Exploration of the Fortieth Parallel led by Clarence King, and the 1875 expedition to the Black Hills directed by W. P. Jenney and Henry Newton. The Hayden surveys took place between 1867 and 1879. Initially funded by federal monies granted to Nebraska Territory, then by the Sundry Civil Bill, they came under the authority of the Interior Department in 1869, when they became known as the U. S. Geological Survey of the Territories. The Hayden surveys are notable for their vast quantity of descriptive information that was published promptly following each field season. Hayden was quick to recognize the value of pictorial as well as written information in his reports, and from 1870 he included Henry Elliot, artist, and William H. Jackson, photographer, in his expeditions. Henry Elliot's sketch of the Sherman granite in the Laramie Mountains may be the first geological sketch of Precambrian rocks in the Rocky Mountains (Fig. 1). Figure 1. Anorogenic granite, Sherman batholith, Laramie Mountains, Wyoming. Elliot's …