St. Croix River as history museum and biology classroom

We strapped on floatation vests the other night and joined National Park Service seasonal ranger Bob Downs for a ride on the river.

We joined Bob and a batch of others including my wife Vicki Olson who snapped all these photos on our evening journey.

Every Wednesday this summer - weather and river conditions permitting - Bob leads a free, one-and-a-half hour tour of a five-mile stretch of the St. Croix.

The starting point is the historic Boom Site landing just north of Stillwater. Bob hits the throttle for a few minutes to head upriver and powers down as we approach the antique steel trestle, still in use, which was a major rail link a hundred years ago for getting the white pine logs from the forest to the sawmills.

Then we turn around, head downriver as Bob points out a heron rookery and an eagle's nest with some young ones watching us.

Then he cuts the engine to talk about river geology.

The evening sun illuminates the river bank's layers of stone and the trees that have sprung up after the white pine clear cutting, which peaked in 1890 and mostly ended in the early 1900s.

Bob is full of lore and biological facts about the river, and here I am taking it all in, including his description of river bluff pictographs painted by the first residents hundreds of years ago. You can hear some of Bob's tour tonight on All Things Considered in my latest Minnesota Sounds & Voices offering.

Words and photos don't capture the therapeutic effects of being on the river and enjoying the splendor of this precious gem. Try to find time this summer to take in one of the free Wednesday evening tours or just make a beeline on your own to take in the sights and sounds.

• In a few years, the nation's tallest building may not be in New York or Chicago
• Cop-suit payouts higher in Minneapolis than Baltimore
• New Minneapolis logo: Now with fewer sailboats
• St. Paul saves dilapidated billboard