The Caves of Mushroom Valley


Photos by Brian Kaufenberg. Historical Photos courtesy of Minnesota Historical Society and Ramsey County Historical Society

According to the boast, it was the mushroom capital of the Midwest. “Mushroom Valley” was the informal name for several miles of the Mississippi River gorge in St. Paul, including what are now Plato, Water, and Joy Streets. The mushrooms were grown in the more than 50 caves dug out of the soft St. Peter Sandstone bluffs. Although called caves, they were man-made, often beginning as silica (sand) mines and later used for various purposes. One cave operated by the Becker Sand & Mushroom Company was the largest of all with 35-foot ceilings and nearly a mile of passages. Its wonderful hybrid name epitomized the valley and the multiple uses of the caves found there. Other uses included the aging of blue cheese, lagering, storage, and even nightclubs.


Interviewed by newspaper columnist Gareth Hiebert (“Oliver Towne”) in 1962, the St. Paul mushroom farmers said their predecessors began the local industry in the 1880s. The original mushroom farmers were said to be Frenchmen who “had seen mushrooms growing in the caves under the sewers of Paris.” Germans and Italians soon joined the mix.

An article in the St. Paul Pioneer Press, May 27, 1923, by Jay W. Ludden, offers a unique glimpse of mushroom farming in its heyday. Ludden was awed by the sheer size of St. Paul’s mushroom caves. “These caverns have cathedral-like arches, and looking into them through the dusk that conceals details and accentuates the big lines, one is reminded of etchings of the interiors of medieval temples. This impression is strengthened when at the distant end of the cave the workmen’s lamps give light as from an altar.” But Ludden reported wars among the mushroom farmers. In one nasty case, a mushroom cave was prevented from expanding further into the sandstone by another mushroom cave that had burrowed completely around it.


Further changes since Ludden’s day improved the lot of mushroom farmers, at least for a while. The adoption of the “tray system” in the 1930s was a big step forward in controlling mushroom pests and replaced the old “floor bed” method of growing mushrooms directly on the fertilized soil of the cave floor. Indeed, remains of these wooden trays are the chief artifact of former mushroom caves in St. Paul.

The mushroom caves were considered for bomb shelters during World War II, even before the Pearl Harbor attack. In the early 1960s, they were surveyed by TKDA, a local engineering firm, for suitability as fallout shelters. This survey produced the only maps we have today. Generalizing from the TKDA survey, the typical cave is a straight, horizontal passage about 150 feet long but often connected by cross-cuts to similar caves on either side, creating mazes with multiple entrances.

“A whole economy and countless legends lie locked from view inside those rustic cliffs.”

– Oliver Towne

Changing circumstances over the years proved difficult for the urban mushroom industry. An article, “Mushroom Farming is Family Tradition,” in the Pioneer Press, March 28, 1976, paints a portrait of Mushroom Valley in its final days. “Mushroom growing,” according to one of the farmers, “remains hard and backbreaking work because some things simply cannot be mechanized, including the picking of mushrooms.” Another problem was the replacement of horses by automobiles, eliminating the farmer’s ready access to cheap horse manure, which was used as the growing medium. Indeed, William Lehmann, known as the “Mushroom King,” had already relocated his Mushroom Valley operation to “the world-renowned cement-block caves of Lake Elmo” in 1965. The rural setting made for lower manure expenses than the heart of the city. The last farmers were forced to vacate Mushroom Valley in the 1980s during the creation of Harriet Island-Lilydale Regional Park. Thus ended a century of production in Mushroom Valley.


Another food industry thrived in the valley alongside the mushrooms. A newspaper reported that Willes Barnes Combs, Professor of Dairy Industry at the University of Minnesota, “found that Roquefort conditions are approximated in the sandstone caves along the Mississippi in the Twin Cities area.” St. Paul’s caves, according to Combs, were “the only caves in this country where temperature and humidity are similar to those in France.” A crucial problem was to hold the temperature low while maintaining high humidity, a seemingly paradoxical combination.

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