Fort Columbia State Park in Chinook.

The U.S. Coast Guard’s presence is only the latest in a long line of U.S. military history at the mouth of the Columbia River.

Both sides of the river have been home to military installations, and at Fort Columbia State Park you can see one of the most complete historic forts in the region.

Situated at a strategic point overlooking the water on the Washington state side, the site was once one of several Chinook villages along the river. Fort Columbia began construction in the late 1890s, and was completed in 1904. It was active all through World War II, though the Japanese submarine that fired on Fort Stevens across the river did not engage Fort Columbia.

In 1947 the fort was declared surplus before being transferred to Washington State Parks, who opened it to the public in 1951. It features its three original concrete artillery batteries, equipped with a variety of defensive equipment including disappearing guns that were lowered into a recess for reloading. The World War II-era Battery 246 has two concrete gun shelters; the guns within are two of only six of their type left in the world.

What makes Fort Columbia unique is that almost all the original wooden buildings, including officers’ quarters, barracks and other fort buildings, are intact. Some are still inhabited by park staff, and two — Scarborough House and the Steward’s House — are used today as vacation rentals. The commanding officer’s house is now the interpretive center, staffed by volunteers 11 a.m. to 3 p.m. every day from July 1 to Sept. 5.

Visitors can explore the batteries (with care), and walk the streets amid the historic quarters. Over 2 miles of trails uphill from the fort offer views and natural wonders. A Washington state Discover Pass is required; a day pass can be purchased at the kiosk in the parking area.