State Route 201 (SR-201) is an east–west expressway and freeway located in Salt Lake County in the U.S. state of Utah. Colloquially known by some as the 21st South Freeway, the route serves as an alternative to Interstate 80 (I-80) through Salt Lake City. From the western terminus of the route west of Magna, the highway heads east through Kennecott Copper property as an expressway before running through the western suburbs of Salt Lake City as a freeway. Shortly after the route returns on a surface route, SR-201 terminates on its eastern end at State Street (U.S. Route 89). The history of the route predates the invention of the automobile; the Donner Party, California Trail and Pony Express all followed the present-day path of the highway. During the 1910s, the route was designated a state highway and, in 1939, State Route 201 was officially written into law, running from Magna east to the mouth of Parley's Canyon. At one point, the highway carried US-50 Alternate west of State Street and both US-40 and US-40 Alternate east of that road, though all were truncated from Salt Lake City by the late 1970s. Construction of the freeway portion of SR-201 west of I-15 commenced in the mid-1960s and was fully completed by 1986. Route description At its western terminus, SR-201 begins at a partial interchange at I-80. Heading generally east with two lanes in each direction, the expressway passes by the Kennecott Smokestack, the tallest structure in Utah. Past its intersection at SR-202, the route takes a turn to the southeast, bypassing the Kennecott tailings pond. Now exiting Kennecott property, the route exits unpopulated terrain and enters the urban Wasatch Front, beginning with the Salt Lake City suburb of Magna. Past junctions at 9200 West, 8400 West, 8000 West and 7200 West, the route veers northerly three blocks and becomes a limited-access freeway. East of 7200 West, SR-201 is routed at approximately 2100 South in Salt Lake County's grid system, giving the freeway its nickname of "21st South Freeway". Now with three lanes in each direction, the highway straddles the boundary between Salt Lake City and West Valley City, another suburb of the former. The road continues due east with diamond interchanges at 5600 West (SR-172) and Bangerter Highway (SR-154). Immediately following a single-point urban interchange (SPUI) at 3200 West, the freeway intersects I-215 in the form of a cloverleaf interchange. The