Issaquah (/ˈɪsəkwɑː/ ISS-ə-kwah) is a city in King County, Washington, United States. The population was 40,051 at the 2020 census. Located in a valley and bisected by Interstate 90, the city is bordered by the Sammamish Plateau to the north and the "Issaquah Alps" to the south. It is home to the headquarters of the multinational retail company Costco Wholesale Corporation. Issaquah is included in the Seattle metropolitan area.

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"Issaquah" is an anglicization of the Southern Lushootseed placename /sqʷáxʷ/, meaning either "the sound of birds", "snake", or "little stream". "Squak Valley", an older name for the area, also derives from this same Native American name.

In September 1885, the then-unincorporated area was the scene of an attack on Chinese laborers who had come to pick hops from local fields. Three of the laborers died from gunshot wounds; seven attackers were indicted, but they were later acquitted or charges were dropped.

Shortly after becoming known as Squak, the town was briefly renamed to Gilman, an homage to Daniel Hunt Gilman, who brought railways to the town.

The city was officially incorporated by the Washington State legislature on April 29, 1892. Initially a small mining town, the city has changed noticeably both in its appearance and economic focus. Issaquah was originally developed to service the mining industry (on the two nearby mountains that now lend their names to the Cougar/Squak Corridor Park), and began as the town of "Gilman". As the mining deposits neared depletion in the late 1890s, other companies started to realize Issaquah's potential to support a lucrative lumber business. These companies exported timber from Issaquah and other small, local towns to Seattle and larger, rapidly growing communities throughout western Washington. These early boom industries, however, faded into a period of relative quiet by the time of the Great Depression.

The town's industries remained similar through most of the century, with Boeing providing the majority of employment in the area. Microsoft and other technological industries moved into Redmond and other cities in the area, and later established operations in Issaquah itself. In June 1996, Costco moved its global headquarters to Issaquah from nearby Kirkland.

Issaquah is located 15 miles (24 km) east-southeast of Seattle at the south end of Lake Sammamish. Its neighboring cities are Bellevue to the west and Sammamish to the north. Issaquah resides within the Mountains to Sound Greenway.

According to the United States Census Bureau, the city has a total area of 11.40 square miles (29.53 km), of which 11.38 square miles (29.47 km) are land and 0.02 square miles (0.05 km) are water.

Issaquah is surrounded on three sides by what are known locally as the Issaquah Alps: Cougar Mountain on the west, Squak Mountain to the south, and Tiger Mountain to the southeast. To the north of Issaquah is Lake Sammamish. Cougar and Squak Mountains are home to sizable neighborhoods on their lower slopes, though the bulk of all three mountains are preserved in public ownership as Squak Mountain State Park, Cougar Mountain Regional Wildland Park, West Tiger Mountain NRCA, and Tiger Mountain State Forest. Geologists have noted the chemical and geological content of these three mountains to be much different from that of the Cascade Range, because they are not volcanic in origin, while the entire Cascade Range is postulated to have formed from volcanic action. They believe that these three mountains are the remains of a much older mountain range long since eroded by earthquakes, volcanic action, and shifting plates.

Issaquah has a warm-summer Mediterranean climate (Köppen: Csb) with chilly, extremely wet winters and warm, moderately humid summers. Although there is no dry season in Issaquah, winters are many times wetter than the summers. Rainfall amounts are extremely similar to the neighboring city of Sammamish, which is 0.06 inches wetter overall, with the same summer rain amounts.

Warehouse retailer Costco has been headquartered in Issaquah since 1996. Other major Issaquah employers include Microsoft, Siemens Medical Solutions' Ultrasound Group, Overtime Technologies, Boehm's Candies, and Darigold. Apparel wholesaler SanMar is also headquartered in the city.

Historical population

Census	Pop.	Note	%±
1900	700		—
1910	628		−10.3%
1920	791		26.0%
1930	763		−3.5%
1940	812		6.4%
1950	955		17.6%
1960	1,870		95.8%
1970	4,313		130.6%
1980	5,536		28.4%
1990	7,786		40.6%
2000	11,212		44.0%
2010	30,434		171.4%
2020	40,051		31.6%
2022 (est.)	39,344		−1.8%
U.S. Decennial Census 2020 Census

According to a 2021 estimate, the median income for a household in the city was $132,984, and the median income for a family was $115,814. The per capita income for the city was $78,581.

According to the Washington State Office of Financial Management, Issaquah ranked 6th of 279 eligible incorporated communities in population growth between 2000 and 2005. Forbes.com ranked Issaquah the 2nd fastest-growing suburb in the state and the 89th in the nation.

As of the 2010 census, there were 30,434 people, 12,841 households, and 8,018 families residing in the city. The population density was 2,674.3 inhabitants per square mile (1,032.6/km). There were 13,914 housing units at an average density of 1,222.7 per square mile (472.1/km). The racial makeup of the city was 74.7% White, 1.4% African American, 0.4% Native American, 17.5% Asian, 0.1% Pacific Islander, 1.8% from other races, and 4.1% from two or more races. Hispanic or Latino of any race made up 5.8% of the population.

For the same census period, there were 12,841 households, of which 33.0% had children under the age of 18 living with them, 51.9% were married couples living together, 7.9% had a female householder with no husband present, 2.7% had a male householder with no wife present, and 37.6% were non-families. 30.1% of all households were made up of individuals, and 10.9% had someone living alone who was 65 years of age or older. The average household size was 2.34, and the average family size was 2.95.

The median age in the city was 36.8 years. 23.7% of residents were under the age of 18; 5.5% were between the ages of 18 and 24; 35.5% were from 25 to 44; 22.6% were from 45 to 64; and 12.7% were 65 years of age or older. The gender makeup of the city was 47.7% male and 52.3% female.

The population has increased by 40,058 people as of the 2020 census.

As of the 2000 census, there were 11,212 people, 4,840 households, and 2,908 families residing in the city. The population density was 1,330.9 people per square mile (514.1/km). There were 5,195 housing units at an average density of 616.7 per square mile (238.2/km). The racial makeup of the city was 87.95% White, 0.88% African American, 0.63% Native American, 6.04% Asian, 0.11% Pacific Islander, 1.46% from other races, and 2.93% from two or more races. Hispanic or Latino of any race made up 4.95% of the population.

There were 4,840 households, out of which 29.5% had children under the age of 18 living with them, 47.3% were married couples living together, 9.6% had a female householder with no husband present, and 39.9% were non-families. 31.0% of all households were made up of individuals, and 7.8% had someone living alone who was 65 years of age or older. The average household size was 2.27 and the average family size was 2.87.

In the city the population was spread out, with 22.2% under the age of 18, 7.3% from 18 to 24, 36.5% from 25 to 44, 24.0% from 45 to 64, and 10.0% who were 65 years of age or older. The median age was 37 years. For every 100 females, there were 91.9 males. For every 100 females age 18 and over, there were 88.1 males.

The median income for a household in the city was $57,892, and the median income for a family was $77,274. Males had a median income of $55,049 versus $36,670 for females. The per capita income for the city was $34,222. About 3.4% of families and 4.8% of the population were below the poverty line, including 5.5% of those under age 18 and 4.7% of those age 65 or over.

Issaquah is bisected by Interstate 90, which runs from Seattle to Boston, and Washington State Route 900, which connects the city to neighboring Renton. There is a chronic traffic congestion problem on Front Street, which traverses the historic downtown. Proposals have been made to create a bypass, but opponents have argued that this will only result in more sprawl in the area beyond downtown and thus bring in more traffic and pollution. In 2008, the Issaquah City Council voted to cancel the 15-year-running SE Bypass project. In addition, King County has no funding in its seven-year capital plan to improve Issaquah-Hobart Road, the southern terminus of the proposed bypass.

Bus service in Issaquah is provided by King County Metro as well as regional Sound Transit routes to Seattle and Bellevue. There are two primary park-and-rides in the city, at Issaquah Transit Center and Issaquah Highlands Park & Ride, which have a total of 1,999 parking spaces.

Since August 1995, the city and King County Metro provided a free circulator bus (route 200) between business districts and community centers in Issaquah as a form of traffic congestion relief.

As part of the expansion of Sound Transit services, a Link light rail line to Issaquah from Bellevue is proposed to begin service by 2041.

The Issaquah Alps are a range of highlands situated around the city of Issaquah that include hiking trails and other outdoor activities. It is primarily composed of three distinct peaks: Tiger Mountain, Cougar Mountain, and Squak Mountain. Paragliders and hang gliders launch from Poo Poo Point on Tiger Mountain in the Issaquah Alps. Several popular trailheads in the area are served by Trailhead Direct, a shuttle bus service managed by King County Metro.

The Issaquah Valley Trolley is a heritage trolley operated by the Issaquah Historical Society on a section of the city's remaining railroad tracks from the Issaquah Depot to Gilman Village. A pilot was organized from 2001 to 2002 with cars borrowed from Yakima Valley Trolleys and followed by the Issaquah Historical Society's acquisition of their own three cars in 2010. Regular public rides started in October 2012 and operated seasonally on weekends until November 2020.

The Village Theatre has presented live stage plays on its main stage in downtown Issaquah since 1979. It was originally located in a converted movie theater and later built its main stage at the Francis J. Gaudette Theatre in 1993. Village Theatre is an Equity theater and has an affiliated theater in Everett.

The Issaquah Salmon Hatchery on Issaquah Creek is a state-owned fish hatchery that was built in 1936 by the federal Works Project Administration. It annually raises about Chinook and Coho salmon and is the most visited hatchery in Washington with an estimated 350,000 visitors annually.

Issaquah Salmon Days is an annual two-day festival held in Issaquah during early October to celebrate the return of spawning salmon to the area. It includes a parade, arts and crafts conventions, live entertainment and music, and sporting events. In 2005, the register revealed over 400,000 people attended the Salmon Days Festival.

The Cougar Mountain Zoo is located on 8 acres (3.2 ha) west of Issaquah on the north slope of Cougar Mountain. The zoo was founded in 1972 and is home to many endangered birds and animals, as well as cougars, lemurs, reindeer, and wallabies. In 2007, the zoo added two Bengal tiger cubs who had been raised in a Florida preserve.

Gilman Village is a shopping center created in 1972 from historic residential and commercial buildings that were moved and renovated for use as independent shops and restaurants. The complex has 27 buildings with various businesses, including specialty shops. The shopping center was designed by Baylis Architects, Richard Haag Associates, and landscape architect Stephen G. Ray.

The High Alpine Chapel opened in 1981 on the grounds of the Boehm's candy shop near downtown Issaquah. It was designed to resemble a 12th-century Swiss church and can hold 57 people. The chapel includes a memorial to deceased mountaineers.

The City of Issaquah uses the mayor-council form of government. The City Council acts as the legislative body. The City Council consists of seven councilmembers, who each have four-year terms in staggered tranches.

Mary Lou Pauly was elected mayor of Issaquah in 2017 with 64.19% of the vote. She was re-elected in 2021 to another term.

In 2023, Issaquah became the first Washington city to be awarded LEED Gold certification for its environmental conservation and sustainability initiatives.

Public education for 21,358 students within the city and surrounding area is provided by the Issaquah School District, which operates 28 schools in and around Issaquah. This school district includes the southern part of Sammamish with the zip code 98075. This area also includes the northern part of Renton.

Swedish Medical Center opened a full-service hospital and healthcare facility in the Issaquah Highlands with a capacity of 175 inpatient beds and a 24-hour emergency room in November 2011. The campus also includes medical offices and specialty care facilities. Bellevue-based Overlake Hospital Medical Center also petitioned the state government to open a hospital in Issaquah, but lost to Swedish's bid.

• Sunndal, Norway
• Chefchaouen, Morocco (since 2007)

• Issaquah-Sammamish Reporter

• Issaquah travel guide from Wikivoyage
• City of Issaquah official website
• Issaquah Historical Society