“In the bowels of U.S. Bank’s basement in downtown St. Paul, Kenton Spading follows guard Linda Traen into the carpeted vault lined with rows of safe deposit boxes. She reaches up to the second row from the top and unlocks a steel door. Spading delicately withdraws a large photo album containing 137 historic photos of the Mississippi River taken in the 1880s.

"They’re in pretty remarkable shape, considering they bounced around on a dredge for more than 50 years,” said Spading, a hydrologic engineer with the U.S. Army Corps of Engineers.

Remarkable - and valuable.

A photography expert from Sotheby’s, the international auction house, flew in from New York recently and spent a day with the old photo album before appraising it at $4.5 million.

For a few Henry Peter Bosse aficionados, including a great-nephew who lives in Minneapolis, the whopping appraisal came as little surprise. But to the rest of us, the value placed on old album raises a few questions:

Who in the heck was Bosse (pronounced BOSS-ee)? Did his obscurity contribute to a string of misfortunes for his artwork, with albums vanishing and glass negatives shattered?

What’s a governmental branch such as the Corps of Engineers doing with such a valuable book? And what’s next for Bosse’s serene, oval cyanotype images of the Mississippi cast in a moody, bluish light from an ancient photographic process?“