Glaciers and proximity to the sea have shaped the landscape of San Juan Island National Historical Park. From American Camp’s South Beach to English Camp’s 650-foot Young Hill, the park’s varied landscapes are the legacy of repeated glaciation.

Landforms include terraced hillsides, moraines, bluffs and dunes of glacial till, old raised beaches and glacial erratics. Ancient bedrock is exposed along a stretch of headlands at American Camp and outcrops at the top of Young Hill. Two brackish lagoons are separated from Garrison Bay by shifting sand/gravel dunes.

Shoreline in the park varies from long stretches of sand/gravel beaches, to rocky headlands interspersed with coves and pocket beaches, to a tranquil, deep bay with mudflats at low tide. The varied landforms of the park support a variety of ecosystems and biological communities that can be explored and enjoyed by all.