Stillwater  itself is the most interesting attraction, and you should plan to spend a good deal of time admiring the 1931 Stillwater Lift Bridge (Chestnut St. E. and St. Croix Trail) and wandering the well-preserved Main Street.
Watching the grand paddlewheelers cruise up and down the St. Croix River is one of the most enjoyable parts of a visit to Stillwater, but it’s even better to be on one. St. Croix Boat & Packet Company (525 Main St. S., 651/430-1234, www.stillwaterriverboats.com , daily May–Oct.) offers a variety of lunch, dinner, and sightseeing cruises, priced from $18.
The Washington County Historical Society’s Warden’s House Museum (602 Main St. N., 651/439-5956, www.wchsmn.org , 1–5 p.m. Thurs.–Sun. May–Oct., $5 adults) was the home of the heads of the now closed Stillwater Prison. Though the house dates from 1853, the furnished rooms appear as they would have in the 1890s, while others hold lumber-era and similar historical displays. The prison room includes an exhibit on the most famous inmates, the Younger Brothers, the other half of the infamous James-Younger Gang.
Hear stories of the city’s history on a half-hour walk through the Joseph Wolf Caves (402 Main St. S., 651/292-1220, 5 p.m. Thurs., 11 a.m. and noon Sat., 11 a.m. Sun., by appt. for groups of 25 or more, $5 adults), which were used to brew beer in the late 1800s, and have also served as a bomb shelter. The Main Street Steps next to the caves lead to a wonderful and oft-photographed view of the city and river.
Explore the river on a pontoon rented from Stillwater Boat Rentals (575 Main St. N., 651/439-9000, www.stillwaterboatrentals.com , 8 a.m.–7 p.m. daily May 15–Sept. 30, from $255 half-day).
You can also ride smaller—much smaller boats—on the river, namely the two-passenger gondolas of Gondola Romantica (425 Nelson St. E. on the riverfront, 651/439-1783, www.gondolaromantica.com ). Rides on the Venetian-style boats poled by burly men in striped sailor’s shirts start at $95 for 45 minutes. Packages combining a ride with a meal at The Dock Café (425 Nelson St. E., 651/430-3770, www.dockcafe.com ) are also available.
The replica Stillwater Trolley (400 Nelson St. E., 651/430-0352, www.stillwatertrolley.com , daily May–Oct., $12.50) zips up and down city streets giving 45-minute narrated tours.
Hot air balloons are an increasingly popular way to take in the valley. Aamodt’s Hot Air Balloon Rides (651/351-0101 or 866/546-8247, www.aamodtsballoons.com ), Stillwater Balloons (651/439-1800, www.stillwaterballoons.com ), and Wiederkehr Balloons (651/436-8172) all soar over the St. Croix from near Stillwater .