Millcreek is a census-designated place (CDP) and township in Salt Lake County, Utah, United States. In the 2000 census, this area was divided among four CDPs, the westernmost of which was designated Millcreek CDP. The population of this CDP was 30,377 at the 2000 census. Canyon Rim CDP, East Millcreek CDP, and Mount Olympus CDP have since been consolidated with Millcreek CDP in the 2010 census, doubling its population to 62,139.
Millcreek Township is an administrative subentity of Salt Lake County that includes the populated Millcreek CDP as well as undeveloped Mill Creek Canyon in the Uinta-Wasatch-Cache National Forest immediately to the east. The township was created by the county in 2002 to give residents of the area more local control over planning and prevent annexations by neighboring cities.
Suburban in character, Millcreek is wedged between Salt Lake City and South Salt Lake on the north and Murray and Holladay on the south. Millcreek residents typically identify with Salt Lake City, which is designated by the U.S. Postal Service as the “default” place name for mailing addresses in the area. However, “Millcreek” is now an accepted place name for addresses in the ZIP codes 84106, 84107, 84109, 84117, and 84124. It is by far the most populous unincorporated area of Salt Lake County, and would be its fifth-largest city if incorporated. Amalgamation with South Salt Lake has also been proposed, which would combine South Salt Lake's commercial and industrial base with Millcreek’s heavily residential character, creating a city of over 80,000.
The incorporation of Millcreek was the subject of a contentious 2012 ballot question, which set the boundaries of the proposed city identical to that of Millcreek Township, and asked voters what form of municipal government should be implemented. The initiative failed with only 40 percent of the vote, leaving Millcreek under the jurisdiction of the Salt Lake County Mayor and Council, as are the other unincorporated areas of the county. The area is organized into four community councils, Canyon Rim, East Millcreek, Millcreek, and Mount Olympus, roughly corresponding to the former CDPs.