Aerial Lift Bridge - Duluth, MN
Posted by: 
FSU*Noles
N 46° 46.735 W 092° 05.575
15T E 569245 N 5180995
Quick Description: This is the Aerial Lift Bridge in Duluth, MN - one of Minnesota's most beloved landmarks, and listed on the National Register of Historic Places as Structure #73002174.
Location: Minnesota, United States
Date Posted: 8/10/2008 5:14:48 PM
Waymark Code: WM4DYJ
Views: 147
Long Description:The Aerial Lift Bridge is the most visible and famous landmark in
Duluth. The span is a vertical lift bridge, but it began life as an
extremely rare transporter bridge — the first of just two such
bridges ever built in the United States. Originally built in 1905,
the bridge was upgraded in 1929–30 to the current lifting design
and continues to operate today.
The bridge spans a small canal which was put through the thin
but long sand bar named Minnesota Point (commonly referred to as
Park Point) in 1870–71. The natural mouth of the St. Louis River is
about seven miles farther southeast, and is split between Minnesota
and Wisconsin. Creating this gap in the tiny peninsula meant that
residents who lived on the new island needed to have a way to get
across. Several different transportation methods were tried, though
they were complicated by the weather: Ferries could work in the
summer, but ice caused problems in colder months.
In 1892, a contest was held to find a solution. The winning
design came from John Alexander Low Waddell, who drew up plans for
a high-rise vertical lift bridge. The city of Duluth was eager to
build the bridge, but the War Department objected to the design,
and the project was canceled before it could be built. Waddell's
design went on to be built in Chicago, Illinois as the slightly
larger South Halsted Street Bridge.
New plans were later drawn up for an aerial transfer, ferry, or
transporter bridge, which had first been demonstrated in Bilbao's
Vizcaya Bridge in 1893 as well as one in France in 1898. Duluth's
bridge was inspired by the French bridge, though the actual
construction is quite different.
When it was completed in 1905, the Aerial Bridge's gondola had a
capacity of 60 short tons (54 tonne) and could carry 350 people
plus wagons, streetcars, or automobiles. A trip across the canal
took about one minute, and the ferry car moved across once every
five minutes during busy times of the day. However, a growing
population on Minnesota Point, a greater demand for cars, and an
increase in tourism soon meant that the bridge's capacity was being
stretched to the limit. A remodeling was planned that would
incorporate a lifting platform into the structure. Ironically, the
firm finally commissioned with designing the new bridge was the
descendant of Waddell's company, and the design is attributed to
C.A.P. Turner.
In order to ensure that tall ships could still pass under the
bridge, the top span had to be raised to accommodate the new deck
when raised. The support columns on either side were also modified
so that they could hold new counterweights to balance the weight of
the lifting portion. The new design closely resembled the original
concept put forth in 1892. The modern structure went into operation
in 1930 on March 19.
The bridge can be raised to its full height in about 3 minutes,
and goes up 25 to 30 times daily during busy parts of the shipping
season. The span is about 390 feet, or 120 meters. As ships pass,
there is a customary horn-blowing sequence which is copied back.
Long-short-long-short means to raise the bridge, and
Long-short-short is a friendly salute.
Source: modified from Wikipedia.
