Thurston County is situated within the southern part of western Washington on the terminus of Puget Sound. It is the thirty second largest county in the state, with a complete land mass of 737 square miles. As of 1995, nearly 93 p.c of the land area was unincorporated.

The world topography ranges from coastal lowlands to prairie flatlands to the foothills of the Cascades. Glacial exercise in the County's geologic previous left the land dotted with lakes and ponds. Quite a few rivers and small tributaries end in Thurston County and drain into Puget Sound. The northern-most boundary of the County is set by the shoreline of Puget Sound. Inlets unique to the County are the Budd, Henderson, and Eld Inlets. Budd and Henderson Inlets are separated by Dana Passage. Other inlets form the boundaries between Thurston and adjacent counties. Totten Inlet divides Thurston and Mason counties, and the Nisqually River separates Thurston from Pierce County.

While a lot of Thurston County's remaining topography is wooded prairie, the northwest and southwest corners are marked by peaks starting from 1700 to 3000 toes in elevation. As soon as thought to be the best within the County, Larch Mountain and Capitol Peak, both over 2650 feet, reign over the forty,000 acre Capitol State Forest west of Olympia. USGS surveyors not too long ago found the very best level in the County is actually within the extreme southeast nook close to Alder Lake. Standing at 2922 feet, Quiemuth Peak was named in 1993 by the Thurston County Historic Commission to honor the Nisqually Indian chief who, with his brother, Chief Leschi, contributed much to the County's early history.

Roughly sixteen% of the land within the county is taken into account farmland. Glacial till and glacial outwash deposits cowl the Puget Sound Valley. Many soils have almost black, brittle, organic-wealthy surface horizons and are often moist in winter but dry in summer. A lot of the land is forested, and lumbering is a crucial industry. The world supports crops or improved pasture, prairie vegetation in some locations, and savanna vegetation in others. Douglas Fir is the dominant tree species. Big Leaf Maple, Western Pink Cedar, Grand Fir and Western Hemlock also are common.