The city lies along State Route 527 and North Creek, a tributary of the Sammamish River, on the east side of Interstate 5.

The Mill Creek area was originally settled in the early 20th century by various farming families, from whom several local placenames are now derived.

[5] In 1931, Doctor Manch N. Garhart acquired 800 acres (320 ha) in the area and used it to grow Gravenstein apples and Bartlett pears while also raising cattle.

[8][9] The Garhart property, along with several neighboring farms, were optioned by various real estate developers in the 1960s and 1970s as a potential master planned community due to its proximity to the recently completed Interstate 5.

[13] A homeowners association was established in December 1974 with funding from United Development to manage the area's security patrol, street maintenance, and other tasks.

[20][21] The first set of homes were designed to resemble country residences, with large floorplans and prominent use of wood furnishings, and sold for an average of $65,000 (equivalent to $348,000 in 2023 dollars).

[22][23][24] Tokyu Land Development later re-used these home designs for the domestic market in Japan, where they were sold under the "Mill Creek" brand in the 1990s.

[17] A majority of the first phase's 1,767 homes and condominiums were completed by early 1983, when an incorporation petition was submitted by residents after reaching the population threshold of 3,000 needed for cityhood.

[18] At the time, the homeowners association and county government had already provided much of the area's infrastructure and maintenance requirements, but local residents resisted attempts to raise property tax assessments.

[18] Mill Creek was officially incorporated as a city on September 30, 1983, ten days after a vote of residents passed, and encompassed 1.92 square miles (5.0 km2).

[28] In the years following incorporation, Mill Creek reduced its property tax rates and formed its own police department, library, postal address, and land-use board.

[30][31] Sid Hanson, the chairman of the incorporation committee, was elected as the city's first mayor and served a single term until declining to run for re-election in 1987.

[36] In 1989, the city proposed a major annexation of 350 acres (140 ha), a 25 percent increase in size, to add undeveloped commercial parcels on the west side of the Bothell–Everett Highway.

[38][39] Everett attempted to annex the entire Murphy's Corner area in the late 1980s, but was forced to split the neighborhood at 132nd Street with Mill Creek after a decision by the state court of appeals and additional arbitration by boundary review boards.

[40][41] The Henry M. Jackson High School was opened in 1994 and is located on the Mill Creek side of Murphy's Corner, which was annexed the following year.

[45] Residents in several potential annexation targets preferred to be left alone by Mill Creek, due to its "snobbish" reputation, which faded as new neighborhoods were absorbed into the city.

[47] The 23-acre (9.3 ha) downtown development would include a large public park, shopping areas, recreational facilities, multi-use trails, and office buildings.

[48] After difficulty in finding a suitable developer,[49] the Mill Creek Town Center began construction in 2001 and the first phase opened three years later.

[56] The retail and residential development, named the East Gateway, would have been located on 52 acres (21 ha) along 132nd Street, and was originally slated to be anchored by a Wal-Mart until the company scrapped plans after protests from local residents.

[63] The city is surrounded by a larger urban growth area that encompasses unincorporated land, including the communities of Martha Lake and Silver Firs, with a population of 68,746 people in 2020.

[68] The original plat of Mill Creek, located east of State Route 527, consists of 21 neighborhood subdivisions that are named for various types of trees.

[72] The Puget Sound Regional Council estimated that the city had a total of 6,262 jobs as of 2018[update], with the largest sectors being professional services and construction.

[71] Mill Creek was ranked 36th on a 2013 Money magazine list of best places to live, based on its quality of life, housing affordability, and school system.

The district encompasses parts of Snohomish and King counties between Arlington and Bellevue that generally lie east of Interstate 5.

[94] Mill Creek is also part of the Snohomish County Council's 4th district, which includes northern Bothell, Brier, and Mountlake Terrace.

[95] Mill Creek hosts a twice-annual community garage sale in May and October that was permitted by the covenants of the original development.

Mill Creek's farmers market runs from June to August and is located in the city hall parking lot.

[101] The golf course at the center of the original Mill Creek subdivision is owned by the members of the private country club, who purchased the facility for $5.2 million in 2007.

[114][115] The Mill Creek branch has 15,000 monthly visitors and the highest hold and pickup rate in the Sno-Isle Libraries system.

[140] A Link light rail extension to Everett is planned to open in 2036 with stations at Ash Way and Mariner Park and Ride near Mill Creek.