Sometimes Thomson Road shows up on maps as Thompson Road.
Some people unfamiliar with their history may wonder what
this bridge is going over, and why an open field is present all of a sudden here also.
MDOT provides a good historic overview of this area, but in short, there used to
be a rail-yard here known as "the hump", which is long gone. The bridge remains
today as a memory of this past. The bridge itself is both old and significant.
The bridge was built in 1919, and is a very early example of t-beam
construction. MDOT mentions that it is also unusual because it did not follow
the state standard t-beam plan that was available at the time.
This bridge is also noteworthy for an attractive brick deck. Brick decks
are surprisingly rare, and very few examples remain today. This bridge retains pole guardrails also. The structure
is slightly skewed, which adds to the technological value of the bridge. As a
five-span bridge, it is also of significant length.
This is one of the few
remaining historic bridges of any kind in Cass County. Despite the fact that it
no longer crosses anything, this bridge is worthy of preservation, both as an unusual structure,
and a memorial to busier railroading times in this area. The bridge is currently
in decent condition, with a 66% sufficiency rating in 2004 in the National
Bridge Inventory, which is very high for a bridge of this age, even on a rural
Thompson Road Bridge is eligible for the National Register as an
excellent example of an early concrete T-beam bridge with very good
historical integrity. This grade separation is among the oldest examples
of a concrete T-beam highway bridge in the state.
The design is quite different from the standard T-beam plan which the
Michigan State Highway Department had developed in the 1913-1914
biennium, but used sparingly during that decade. The plans for the
Thompson Road Bridge were probably developed by the railroad company,
which had a switching yard and many associated tracks in the area. The
tracks under the bridge were originally operated by the Michigan Central
Railroad; later, other companies assumed control over the trackage. The
main line of the Michigan Central, which was built in Cass County in
1848, is about one-half mile west of the bridge site.
After the Civil War, a new railroad called the "Air Line" linked Jackson
with the Michigan Central line at Niles. Within two years, the Michigan
Central controlled the Air Line routes. A 1935 county history notes that
a cut-off was built to connect the Air Line route and the main line of
the Michigan Central in Howard Township "some fifteen years ago." That
date seems to correspond to the 1919 date of the bridge. The wide
right-of-way near the bridge was used as a railroad switchyard known as
This bridge is tagged with the following special condition(s): Unorganized Photos
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