Fort Clatsop National Memorial was established in 1958 to "commemorate the culmination and Winter encampment of the Lewis and Clark Expedition". Fort Clatsop National Memorial is located near the extreme northwest corner of Oregon and encompasses 125.2 acres in three disjunct units. Visitor services are located within the 108 acre larger unit on the west shore of the Lewis and Clark River and the 100 foot by 100 foot Salt Works Site unit situated within downtown Seaside, OR. The third unit of the park is a 17 acre parcel of land located along the east shore of the Lewis and Clark River opposite the main unit. The park is located within three miles of Astoria, the oldest American settlement west of the Rockies, with a current population of approximately 10,000. The topography of the park varies from estuarine mudflats in the Lewis and Clark valley to steeper forested slopes and benches of the eastern toe-slope of Clatsop Ridge, the northern-most portion of the Oregon Coast Range. Elevation ranges from 6 feet to 60 feet. The park’s climate is characterized by relatively warm and dry conditions in the summer and fall and cool, wet conditions in the winter and spring. Rainfall averages approximately 70 inches per year. Although small in size, Fort Clatsop contains diverse wildlife habitat and resources. Park ecosystems range from the estuarine mudflats and tidal marshes, to shrub and forested swamps and upland coniferous rainforest, dominated by Sitka spruce as large as 6 feet in diameter. Ten types of wetlands occur within the park in palustrine, estuarine and riverine systems, as identified by the National Wetland Inventory, and wetlands comprise approximately half the park acreage. Surface water consists of the tidally influenced Lewis and Clark River, low-gradient brackish sloughs, freshwater ponds and small freshwater streams and springs. Approximately 50 acres of the park is coniferous forest habitat, composed of approximately 20 acres of older forests and 30 acres of younger forests. Flora and fauna diversity within Fort Clatsop National Memorial are high, reflecting the park’s habitat diversity, its moderate climate, its location along the Pacific flyway and its proximity to the Pacific Ocean. The replica of the original Fort Clatsop was built in 1955 for the Lewis and Clark Sesquicentennial by local civic organizations. The fort is the nucleus for a variety of interpretive, educational and living history programs throughout the year. The entire park is listed on the National Register of Historic Places.