"F" is for "Fort" and all the forts and their history preserved as or within units of the National Park System.

According to the National Park Service, "In November 1805, the Corps of Discovery reached the Pacific Ocean. Having found 'the most practicable and navigable passage across the Continent of North America,' the mission was complete. Although eager to begin the journey home, members of the Corps knew that travel would have to wait until spring - more than one snowy mountain range stood in their path. The Corps would build a temporary home on the coast."

"In early December, William Clark recorded that Meriwether Lewis had found a suitable location for their winter quarters with 'Elk Suffient to winter on.' Once completed, their home, a fortification measuring just fifty feet square, housed 32 men, 1 woman, a baby, and a dog. On Christmas Day, according to Joseph Whitehouse, '[w]e all moved into our new Garrison or Fort, which our Officers named after a nation of Indians who resided near us, called the Clatsop Nation; Fort Clatsop.'"