Mercer Island is located closer to Bellevue than it is to Seattle, and is therefore often considered to be part of King County's Eastside.

[4] Mercer Island is one of the 100 richest ZIP codes in the US according to the IRS figures for Adjusted Gross Income.

[7] The western side of the island was home to two Snoqualmie villages prior to white settlement in the Puget Sound region.

The Mercer brothers often rowed between the island and Seattle to pick berries, hunt, and fish.

Guests included President Benjamin Harrison, of 1901, amongst other well-to-do dignitaries from Seattle to the East Coast of the United States.

A denser urban community with business district developed toward the central northern island between the McGilvra neighborhood and Luther Burbank Park.

Mercer Island City Hall was located at 47°34′14″N 122°13′19″W / 47.57056°N 122.22194°W / 47.57056; -122.22194 (47.5706548, -122.2220673),[3] until it was closed in April 2023 after asbestos was discovered in the heating, ventilation, and air conditioning system.

This region experiences warm (but not hot) and dry summers, with no average monthly temperatures above 71.6 °F (22.0 °C).

At the national level, Mercer Island is located in Washington's 9th congressional district, which is currently represented by Democrat Adam Smith.

In February 2021, a 6–1 majority of the Mercer Island City Council passed an ordinance prohibiting outdoor camping on public property, mainly to restrict homeless and unhoused people from overnight stays.

The ordinance was criticized by the American Civil Liberties Union of Washington and other public advocates for the homeless.

[25][26] Luther Burbank Park covers 77 acres (310,000 m2) of land and has 0.75 miles (1.21 km) of waterfront.

[citation needed] The park has a public boat dock and fishing pier, a swimming beach, an amphitheater, tennis courts, barbecues and picnic facilities, and an off-leash dog area.

[32] Clarke Beach is located at the south end of Mercer Island and is home to the annual polar bear swim on New Year's Day.

Mercer Island also has many smaller parks maintained by the city, some of which have waterfront access.

In 2010, the city built a well in Rotary Park to supply the area with water in the event of a major disaster, specifically an earthquake.

[34][35] Mercer Island is bisected by Interstate 90, which connects the city to Seattle in the west and Bellevue in the east.

The bridges also carry the Mountains to Sound Greenway, which includes a multi-purpose pedestrian and bicycle path.

A significant section of the freeway is recessed below street level and covered by the Mercer Island Lid, which includes several parks.

[55] The city's public transportation is provided by King County Metro and Sound Transit, mainly consisting of express bus routes to Seattle and the Eastside.

[59][60] In early 2025, a light rail station at the park and ride facility will be opened by Sound Transit, providing service on the 2 Line to Seattle and the Eastside.

[61] The light rail line will replace several express routes on Interstate 90 and Mercer Island is expected to function as a major bus–rail interchange.