Down by the river is the Cascade Locks Marine Park (Exit 44 off I-84 East). Look for it on your left going east on Wa-Na-Pa Street; just follow the signs.
Here the sternwheeler Columbia Gorge (reservations 503/224-3900 or 800/224-3901, www.portlandspirit.com ) makes it possible to ride up the river in the style of a century ago. This 145-foot 330-ton replica carries 599 passengers on three decks. There are several interesting packages of varying themes and duration. The two-hour sightseeing cruise ($28 adults and seniors, $18 children) departure times vary; check the website for schedules. Lunch, dinner, and weekend brunch cruises are also available; cruises run May–October.
Port of Cascade Locks (541/374-8619, www.portofcascadelocks.org ) houses the ticket office as well as an information center and gift shop, which sells an excellent map of local hiking trails.
About 0.25 miles west of the visitors center, Cascade Locks Historical Museum (503/374-8535, 10 a.m.–5 p.m. daily May–Sept., free) is housed in an old lockkeeper’s residence and exhibits Native American artifacts and pioneer memorabilia.
Information about the fish wheel, a paddlewheel-like contraption that conveyor-belted salmon out of the river and into a pen, is especially fascinating. This diabolical device was perfected in Oregon  in the early 20th century and was so successful at denuding the Columbia of fish that it was outlawed.
Outside the museum is the diminutive Oregon Pony, the first steam locomotive on the Pacific coast. Its maiden voyage dates back to 1862 when it replaced the 4.5-mile portage with a rail route around the Cascades.
Take a walk over to the old locks. Begun in 1878 to circumnavigate the steep gradient of the river, they were completed in 1896. By the time the Cascade shipping locks were completed, however, river traffic had decreased because cargo was being sent by train, so the impact of altering the river flow was negligible.