railroad construction. ... The actual benchmarked survey elevation value of the summit of Rollins Pass is 11,671 feet (NGVD29), obtained during a 1952 second-order level line run from State Bridge to Denver by the US Coast and Geodetic Survey (predecessor to the National Geodetic Survey). When adjusted to NAVD88, the elevation is, without doubt, 11,676.79 feet." Description Rollins Pass has been in continuous use for millennia: first as a sprawling and internationally significant game drive complex that was hand-constructed and used by Paleoindians more than 10,000 years ago through the mid-19th century; followed by nearly two decades as a wagon road from 1862–1880; as a rail route (under survey, construction, and later operational) from 1880 to 1928; as a primitive automobile road from 1936 to 1956; and since September 1, 1956 as a seasonal, unpaved motor vehicle road. The pass is traversed by Paleoindians and Native American game drive complexes, hiking trails, including the Continental Divide Trail; an airway radial (V8), a 10" Xcel Energy high-pressure natural gas pipeline, and two roads: The first dirt road is the Rollinsville and Middle Park Wagon Road, created in the early 1860s and this route predates the rail line. This road employed much of what would later become Rollins Pass, particularly above timberline. This original wagon route, now called the Boulder Wagon Road, took a steep counterclockwise route up Guinn Mountain encircling Yankee Doodle Lake before continuing to head west/northwest to proceed over the summit and down into the Middle Park valley near present-day Winter Park and Fraser, Colorado. The second dirt road is mostly the former roadbed of the Denver, Northwestern, and Pacific Railway, that later became the Denver and Salt Lake Railway. This high-altitude railroad grade was part of the Moffat Road and this route was replaced (and later abandoned) by the opening of the Moffat Tunnel in 1928; the rails and ties were removed from Rollins Pass in 1936; however, some rail segments as well as ties, made of pine, oak, and walnut, can still be seen, along with planking used for snowsheds. Geology The Front Range was created by the Laramide Orogeny, the last of three major mountain-building events, which occurred between 70 and 40 million years ago. Tectonic activity during the Cenozoic Era changed the Ancestral Rocky Mountains via block uplift, eventually forming the Rocky Mountains as they exist today. The geologic make-up of Rollins Pass and the