New Ulm’s ‘Underground City’

Photo courtesy of Bolton & Menk Inc., engineering consultants Construction workers installing ‘cattle passes’ along Minnesota Street near 2nd North Street, where the tunnels were once located.

New Ulm’s ‘underground city’/tunnels were commonly known as the ‘steam tunnels’ because the steam lines were placed inside the existing tunnels under the sidewalks of Minnesota Street. The tunnels, however, were not built for the steam lines. The tunnels were built long before the steam lines came into being. New Ulm’s ‘underground city’/tunnels were located under the sidewalks of Minnesota Street from approximately 4th North to 1st South.

In 1924, an informational circular was issued by the City regarding “Facts and Figures Regarding the New Ulm Heating System.” The circular said in part: “The New Ulm Heating System has been in operation since 1916. It was created for the purpose of utilizing the exhaust steam supply of the Municipal Lighting Plant in the heating of the business district of the city, the money required for its construction being furnished entirely by New Ulm business men . . . It was never intended that the system should be extended to cover any large areas . . .”


During the 1960s, a number of studies were completed for a new design proposal for New Ulm’s downtown, called “Marktstrasse” or “market street” . . . also referred to as a new “Streetscape” for downtown New Ulm. This plan included numerous changes to downtown, including the ‘steam tunnels.’

In the early to mid 1990s, after almost 30 years of studies, planning, debate, and delays, the New Ulm “Streetscape” was becoming a reality. One study . . . “New Ulm Steam System Study” conducted by HDR Engineering, Inc. stated in part:

Photo by Elroy Ubl Closed-off remains of stairwell from Minnesota Street. Huge boulders and bricks were used during construction of the tunnel. Note the brick ceiling . . . arched for support and strength.

“The steam mains on Minnesota Street are located in tunnels in generally under the sidewalks and in building basements on both sides of the street. The original tunnel walls are the outside building foundation walls and with the outer tunnel walls constructed of stone. Portions of the tunnels have been replaced with cattle pass, concrete block or poured concrete construction and are in good condition. However, there are approximately 1,1644 feet of tunnel in poor condition which must be reconstructed during the Streetscape Project. It would be unacceptable to have the tunnels in the current condition under the Streetscape as continuing problems would require breaking into the new street and sidewalk surfaces to repair.

“The tunnels in poor condition would be replaced with cattle pass construction with new sidewalks supported on engineered backfill above the tunnels.

“The heating system is located in tunnels under the sidewalks on either side of Minnesota Street or in the basements of adjacent buildings except for a short segment of direct buried piping south of 1st South Street. The tunnels are constructed of rock or concrete blocks with the outside building basement wall forming one side of the tunnel. The top of the tunnel is the sidewalk. In locations where the tunnel deterioration has required replacement, open or closed bottom cattle pass, concrete block or poured concrete construction was used. The cattle pass provides a tunnel about 4 feet wide by 6 feet high at the high point which allows walk-through access to the main. Backfill above the cattle pass supports the sidewalk. Some tunnel construction used concrete blocks with the top of the tunnel forming the sidewalk. Both the cattle pass and new concrete block segments are in good condition. During Streetscape construction, the tops of the tunnels would be removed (except of cattle pass) which will require careful protection of the mains to prevent damage to the main and its insulation. With the tunnels opened up, there will be an opportunity to reconstruct poor segments of the tunnel system.

“In our opinion, it is possible that the stone tunnels may NOT (my emphasis) have been originally installed for the heating system. A substantial portion of the stone tunnel is 9 feet wide which is more than would be required for the steam main and condensate return . . . . Furthermore, the building basement wall which forms the inside wall of the tunnel has, in many cases, doors which access the tunnel and windows (mostly boarded up) but some with glass still remaining which look only into the tunnel. Some merchants use the tunnel space for storage. The ceiling of one segment of the tunnel is a series of red brick arches supported by steel cross members. The steel is badly corroded and shows some signs of distress. It is suggested that the structural integrity of the ceiling be analyzed as it forms the support for the sidewalk above.”


Photo by Elroy Ubl Doorway between the tunnel and the business basement. Note the thickness of the arched doorway/ interior wall of the tunnel. To the left of the doorway is one of the display windows that has been bricked shut (see photo below for the other display window) . . . Yes, display windows! The brick / stone wall at far left is one of the walls constructed to separate or block access to the next business to the south. Prior to these separation walls, ‘pedestrians’ could walk the entire length of downtown Minnesota Street underground, and shop . . . look at the displays in the windows, and enter a business from the tunnel . . . hence, ‘underground city?’

In late 1993, after HDR Engineering, Inc. completed their study I was contacted by Ron Marquardt, City of New Ulm Water/Steam Supervisor, who said: “You may want to take photos of the ‘steam tunnels’ before they are removed/filled in.” Without hesitation, I agreed! We toured the tunnel areas along the west side of Minnesota Street, and entered each area through the basement of retail businesses (see photos and photo descriptions).

The “Streetscape” project included repairs of utilities and sidewalks on five blocks of Minnesota Street . . . Including street, and lighting improvements . . . bringing back the old “White Way” street lights. Also, the ‘steam tunnels’ were replaced (‘steam tunnels’ were blocked off/’filled in’). When the repairs were completed, the tunnels were no longer accessible from Minnesota Street retail basements, and steam valves were moved inside buildings.

At a meeting in 2000, Mr. Robert Stevenson, Director of the New Ulm Public Utilities, explained that New Ulm’s ‘steam tunnels’ were five blocks long and located under the sidewalks of Minnesota Street adjacent to the retail basements. A lot of heat was given away to the businesses. In 1996, when Minnesota Street was rebuilt, the ‘steam tunnels’ were placed closer to the street, away from the basement businesses . . . and the old tunnels were blocked off (filled in). Access today is now through sidewalk hatch/openings into ‘cattle passes’/large concrete culverts/cement block passages.

A number of questions remain: When were the tunnels built? Why were the tunnels built? Who built the tunnels? Who do you ask, or where do you look to find information about the tunnels? Old New Ulm City records, old newspapers, and old maps do not mention the tunnels.


Photo by Elroy Ubl Same tunnel location as Photo above, looking north. Note the bricked-up display window to the right of the doorway . . . and the separation wall to the north, constructed with large boulders. If you look closely at the ceiling, one of the ‘grates’ from the sidewalk above can be seen. Also, many of the businesses used the tunnels next to their basement as a storage area.

A big thank you to Ron Marquardt, City of New Ulm Water/Steam Supervisor, for recognizing the historic importance, and informing me about the underground tunnels. Perhaps a small area/portion of the New Ulm’s ‘underground city’ should have been saved as a unique tourist attraction ?

Photo by Elroy Ubl There was a series of red brick arches supported by steel cross beams in some areas of the tunnels . . . many of the steel beams were badly corroded. The arched brick ceiling were constructed for support / strength. The photo shows the outer wall (street side) of the tunnel . . . again, note the large boulders used to build the wall. The tunnel was approximately 9 feet wide, and 8 feet tall.


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