Lewis and Clark National Historical Park is one of those interesting partnership parks that have evolved in recent decades. It has a core resource -- Fort Clatsop -- directly owned and managed by the National Park Service, and a number of partner sites in the area around the mouth of the Columbia River that are in some way associated with the Lewis and Clark expedition, like Cape Disappointment State Park in Washington. The wayside above, for example, is in Astoria, near the Astoria column.
The views from that location are, to say the least, good.
There are also a fair number of NPS-designed waysides along the waterfront in Astoria, each one providing some insight into local history, the natural environment, and Lewis and Clark. On the Washington side of the river, Lewis and Clark turn up at sites all the way up to Long Beach.
William Clark apparently caught a sturgeon there, as well as observing a flounder for the first time.
Cape Disappointment State Park also features prominently in the Lewis and Clark story. The expedition apparently spent some time in the Cape Disappointment area debating whether they should remain on that side of the river for the winter, or move to the south bank.
Cape Disappointment State Park covers about 5,000 acres, includes 2 lighthouses (Cape Disappointment and North Head), and has the usual hiking trails and campgrounds in addition to the late 19th century military fortifications and a really nice visitor center. Fort Canby was built to protect the mouth of the Columbia River, as was Fort Stevens on the Oregon side. From whom, I'm not sure, but apparently someone felt vulnerable.
The original plan for the fort was to place the guns right next to the Cape Disappointment Lighthouse, right about where that Jeep is sitting in the photo. The visitor center had a nifty circa 1895 photo showing the mortars in place, cannonballs stacked neatly next to them, as well as a number of no-longer extant ancillary buildings for the lighthouse (a keepers' quarters to the right of that modern sidewalk, for example). Then they test-fired the largest gun -- and multiple windows shattered. So they moved everything, and built Fort Canby. The lighthouse had a first-order Fresnel lens that's now on display in this building:
This is what Fort Canby looks like now as seen from the lighthouse -- it's the visitor center at the park.