Hike to the Cave Near McGregor City Well Number 6.
Many caves were dug into the Jordan Sandstone by early residents for storage and packed with ice for use as cold storage. One is accessible on McGregor city property near City Well No. 6 (see photo to left). This cave once sheltered up to 20 tons of ice to supply the popular "Mississippi House" hotel and tavern which formerly stood on this site.
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Discussion of the
Jordan Sandstone Caves in McGregor
by Robert McKay, Senior
Research Geologist |
The bluffs of McGregor are festooned with small caves, hewn into Jordan Sandstone by 19th century residents. The residents found that the unusually soft, uniform "sand rock" was easily excavated with hand tools, and that "caves" or "cellars" carved into these sandstones provided ideal space and cool temperatures for refrigeration and storage of river ice. Most of the cellars were excavated in sandstone along the northern end of Main Street, where hotels, taverns, and apartment buildings backed into small courtyards framed by the nearly vertical sandstone bluffs. The cellars varied in size and were entered via arched doorways. Smaller caves, typically associated with taverns and apartments, were about 20 feet deep and housed items ranging from food to ammunition; some functioned as cisterns for water storage.
The Jordan Sandstone is friable but stands well vertically because it is very weakly cemented by minute amounts of silt size dolomite rhombs. These two characteristics made the unit ideal for excavation with simple hand tools by the early settlers of McGregor, and numerous “caverns” and storage rooms were excavated. For more information on the geology of the Jordan Sandstone click here.
Most of McGregor's historic caverns are now inaccessible because of the deteriorating effects of time and weather. As one strolls through McGregor, however, several sandstone entryways remain visible, reminding us of the interesting and historic influence of local geology on the lives of the people who lived there.
To learn more about McGregor's 19th Century Refrigerators see the Geological Survey Bureau's web page at http://www.igsb.uiowa.edu/browse/doors/doors.htm
This is the Official End of GSI Field Trip #70
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