thumb|right|[[Mount Rainier from Ricksecker Point, 1932]]
right|thumb|[[Tacoma, Washington|Tacoma—seat of Pierce County]]
[[File:Mount Rainier Hazard Map-en.svg|right|thumb|Hazard map of Mount Rainier
]]
Pierce County is a county in the U.S. state of Washington. As of the 2020 census, the population was 921,130, and was estimated to be 946,288 in 2025, making it the second-most populous county in Washington, behind King County, and the 60th-most populous in the United States. The county seat and largest city is Tacoma, Formed out of Thurston County on December 22, 1852, by the legislature of Oregon Territory, it was named for U.S. President Franklin Pierce. Pierce County is in the Seattle metropolitan area (formally the Seattle–Tacoma–Bellevue, WA, metropolitan statistical area).
Pierce County is home to the volcano Mount Rainier, the tallest mountain in the Cascade Range. Its most recent recorded eruption was between 1820 and 1854. There is no imminent risk of eruption, but geologists expect that the volcano will erupt again. If this should happen, parts of Pierce County and the Puyallup Valley would be at risk from lahars, lava, or pyroclastic flows. The Mount Rainier Volcano Lahar Warning System was established in 1998 to assist in the evacuation of the Puyallup River valley in case of eruption.
Geography
According to the United States Census Bureau, the county has a total area of , of which is land and (7.61%) is water. It is the 23rd largest county in Washington by total area. The highest natural point in Washington, Mount Rainier, at , is located in Pierce County. Rainier is locally called Tahoma or Takhoma, both native names for the mountain.
Geographic features
- Anderson Island
- Carbon River
- Cascade Range
- Case Inlet
- Commencement Bay
- Fox Island
- Herron Island
- Ketron Island
- Key Peninsula
- Lake Tapps
- McNeil Island
- Mount Rainier, highest point in both the county and Washington state.
- Nisqually River
- Puget Sound
- Puyallup River
- Raft Island
- Tacoma Narrows
Pierce County also contains the Clearwater Wilderness area.
Adjacent counties
- King County – north
- Yakima County – east
- Lewis County – south
- Thurston County – west/southwest
- Mason County – west/northwest
- Kitsap County – north/northwest
- Kittitas County – northeast
National protected areas
- Mount Baker-Snoqualmie National Forest (part)
- Mount Rainier National Park (part)
- Nisqually National Wildlife Refuge (part)