There is a mystery in Cambridge Woods Park on the east bank of the Milwaukee River — an ancient tunnel made from carefully cut and fitted stone blocks and large enough to drive a truck through.
From its portal in a bluff at the foot of Hampshire Street, the tunnel extends eastward under the Oak Leaf Trail only to end abruptly at a modern concrete wall about 60 feet inside the entrance.
Who built it? And for what purpose?
The first question is easy to answer. The second is more elusive.
In the 1880s, the Northwestern Union Railway built a railroad line from the downtown lakefront north through the East Side and Shorewood. Workers cut through hills and filled ravines as they went.
At Riverside Park, the railroad contractor built a stone-lined tunnel underpass to accommodate a carriage drive, which then ran from Newberry Boulevard to the river.
That tunnel was filled in when the Riverside High School athletic field was built in the 1970s, but you can still find traces — if you know where to look.
Further to the north, the railway built two stone tunnels and filled a deep ravine at Shorewood. One tunnel served a creek that drained to the Milwaukee River and the other provided wagon access for an ice harvesting business in what is today Hubbard Park.
The ice operation is long gone, so is the creek, and so, for that matter, is the railroad. (Its former right-of-way is now the Oak Leaf recreational trail.) But the twin tunnels at Hubbard Park, now used by roadways, are still there.
These tunnels are railroad underpasses. They were probably built first and later covered by the fill dirt of the railroad embankment — no tunneling required.
But what of the crumbling remnant in Cambridge Woods? It appears to extend deep into the bluff with no apparent eastern portal. Where did it come out?
When the railroad came through, 130 years ago, Hampshire Street and the surrounding residential neighborhood was still in the future. Most likely, in the 1800s, this was the location of a ravine cutting through the bluff down to the river. Years later, that ravine east of the tracks was filled, leveled, and divided into lots for homes.
The question of why the railroad built this expensive piece of civil engineering remains.
Perhaps there was once a creek, like the one formerly flowing through one of the Hubbard Park tunnels. But I think it is more likely this tunnel provided access to another river ice harvesting operation.
According to the 1879 annual report of the Commissioner of Health of Milwaukee, “The Joseph Schlitz Brewing Company erected five large ice houses on the west bank of the Milwaukee River, about midway between North street bridge and Humboldt (now Capitol Drive), where it will cut a supply of ice sufficient for the requirements of its extensive brewery and bottling establishment.”
As part of this effort, the brewery built a log dam across the river at the foot of East Chambers Street and, on the west side of the river built two large ice houses. This operation was active at the time the railroad was under construction.
The brewery also owned the land on the east bank of the river. In fact, this part of Cambridge Woods Park was donated to the county in 1940 by the owners of the brewery.
In its November 26, 1940, issue, the Milwaukee Journal announced the donation. Included was a parcel between the river and the railroad tracks running from the tunnel north to East Edgewood Avenue. The 2,282-foot-long, eight-acre parcel varied between 150 to 258 feet wide. The newspaper said it was “wholly unproductive property” but ideal for park purposes.
It seems probable the brewery, back in the 1890s, demanded railroad contractors build the underpass to provide access to the Schlitz-owned land on the east side of the river. Did the brewery also maintain an ice house on that side of the river?
Crumbling, partially filled in, but still imposing, the tunnel guards its secrets.