Newcastle is an Eastside city in King County, Washington, United States.

[4] Although Newcastle was not incorporated until 1994, it has been an important settlement and town since the late 19th century and played a major role in the development of Seattle and the surrounding region.

[6] Newcastle was one of the region's first coal mining areas and its railroad link to Seattle was the first in King County.

In CNN Money's 2011 rankings of best places to live in the United States, Newcastle was in the top 20, along with nearby Sammamish.

East of southeast Lake Washington is a large quantity of hilly terrain, which creates opportunities for view properties.

This created the impetus for the location of the Newcastle Golf Course, along with many high-value homes at higher elevations with views of downtown Bellevue, Seattle, and Mercer Island, as well as the Olympic Mountains.

Notable attractions of the area include the Golf Club at Newcastle, a brand new Family YMCA, Lake Boren Park, a well developed trail system, and nearby Cougar Mountain in the east of Newcastle.

[11] The city has an active trail-building community, creating a system of trails that are being integrated into new housing developments and parks.

[12] Most of the trail-work has been completed by volunteers and the Washington Conservation Corps, sponsored by the city of Newcastle.

The trail system will eventually lead all the way to Lake Washington to the west, in conjunction with Renton, and is already connected to Cougar Mountain Regional Wildland Park to the east, which is in unincorporated King County.

The city has not obtained its own ZIP code even though, based on the ZIP code designation, some sales taxes paid by Newcastle residents go to Renton instead of Newcastle as tax revenues (among other perceived detrimental impacts related to mail service, insurance rates, property values, and credit ratings).

considering the small size of Newcastle with a small commercial district which does not create as much property tax or sales tax revenue for the city compared to neighboring cities like Renton to the south, Bellevue to the north, or Issaquah to the east.

Coal Creek flows through the city from the Issaquah Alps to Lake Washington.

Newcastle is bordered to the north by Bellevue, to the south by Renton, to the east by unincorporated land on Cougar Mountain, and to the west by Lake Washington.

[2] Newcastle is served by two school districts, with the boundary line roughly going north–south just to the west of Coal Creek Parkway.

Newcastle has been a preferred residence of numerous current and former Seattle Seahawks players, coaches, and front office personnel[citation needed] due to its close proximity to the NFL franchise's headquarters and practice facility on Lake Washington at the Virginia Mason Athletic Center (VMAC) in Renton.

Designed by golf course architect Robert E. Cupp in consultation with PGA Masters champion Fred Couples and in partnership with Oki Golf, the courses have views of Mount Rainier, Lake Washington, Lake Sammamish, the Olympic and Cascade mountain ranges, and the downtown skylines of the cities of Seattle and Bellevue.

Practice and hospitality facilities include a heated driving range, a pro shop, an 18-hole mini-golf/putting range, private (pitching/putting/chipping) practice tees, and a 44,000-square-foot (4,100 m2) clubhouse with restaurants, pubs, and event spaces.