Nellis Air Force Base, which is north of Las Vegas, at one time had a freight spur that connected to UP's mainline (formerly of the Los Angeles & Salt Lake Railroad). The right-of-way is still visible near the UP mainline; the segment between I-15 and Las Vegas Blvd. has been completely obliterated by the Las Vegas Speedway. Remnants of track are still visible on the Nellis AFB property behind a chain link fence.
Also, contained completely within Nellis AFB, is another set of abandoned tracks; these are to the southwest of the first track, as seen on the map.
Thanks to Mike Palmer for contributing information about this route.