(The original contents of this post has been moved to Frankfort, IN.)

(Bridge Hunter; Historic Bridges; HAER; 3D Satellite)

A video of Paul R. Tregurtha having to do an emergency 360-degree turn because of issues with lifting the span of this bridge was my motivation for finally documenting this bridge. I've seen plenty of YouTube videos of boats passing under the bridge because the boats and the bridge tender generally "salute" each other. Saluting is sounding their horn.

In the above video, you can see the prop wash of the main propeller, but I could not see any prop wash for a bow thruster. The following photo confirms it has a bow thruster marking. So was it able to do that tight turn with just its rudder? That would explain why it maintained power and speed during the turn.

Interlake Steamship Company posted

Hello Twin Ports! Our M/V Paul R. Tregurtha sails under the iconic Duluth Aerial Lift Bridge on her way to Superior to take on more than 60,000 tons of coal. It will take her 2.5 to 3 days to transport the essential cargo to the DTE power plant in St. Clair.  #shippingmatters

: David Schauer

Damian Entwistle Flickr, cropped; License: Attribution-NonCommercial 2.0 Generic (CC BY-NC 2.0)
Duluth - Enger Tower, view to lift bridge

Damian Entwistle Video, cropped; License: Attribution-NonCommercial 2.0 Generic (CC BY-NC 2.0)
Duluth - Enger Tower, lift bridge and laker

Robby Gragg Flickr
Phillip R Clarke
The Phillip R Clarke ducks under the historic aerial lift bridge in Duluth, MN.

The reason for the two dates is that it was originally built in 1905 as the transporter shown in this photo. In 1930, after raising the transporter truss and reinforcing the towers, a lift span was added.

Tom Wigley Flickr, License: Attribution-NonCommercial-ShareAlike 2.0 Generic (CC BY-NC-SA 2.0)

Aerial bridge. Duluth, Minnesota

Circa 1905. "Aerial bridge. Duluth, Minnesota." Suspended Car Transfer over the Duluth Ship Canal. The gondola could carry 60 tons of cargo across the 300-foot channel with minimal obstruction of the shipping lane. After modification for service as a vertical lift, the span became known as the Aerial Lift Bridge. 8x10 dry plate glass negative, Detroit Publishing Company.

Steve Vanden Bosch posted
David Stack: This very unusual aerial ferry configuration of the Duluth canal bridge was in operation from 1905 to 1929.

Bridges Now and Then posted
Onlookers watch the gondola of the Duluth Aerial Transfer Bridge cross the Duluth Ship Canal, 1905. (Library of Congress)

Jerry Bielicki updated
Duluth.......1905
Jerry Bielicki shared
Laura Jacobs: original by photographer Hugh McKenzie.
Gordy Schmitt

Detroit Publishing Company photo, they show a 1908 date on the photo. https://www.loc.gov/resource/det.4a23152/

HAER MINN,69-DULU,9--4, cropped
4. SOUTH ELEVATION OF BRIDGE, WITH THE 'ROGER BLOUGH' HAVING PASSED UNDER - Duluth Aerial Lift Bridge, Lake Avenue, across Duluth Ship Canal, Duluth, St. Louis County, MN

The bridge spans the Duluth Ship Canal, which was dug in 1870 through the sand bar that routed the Saint Louise River further south and east before opening into the lake. The sand spit, commonly called "Park Point" by locals, named Minnesota Point, allowed ships to avoid Superior WI while still getting from the river to Lake Superior. This also turned the peninsula into an island. Ferries worked - but not during icy winter.

In 1892, John Low Waddell designed a high lifting vertical lift bridge. The War department did not approve so Duluth did not get to build it. But the design was modified and built in Chicago as the South Halsted Street Bridge. Thomas McGilvray, a city engineer, drew the plans for the structure that was built, apparently inspired by a similar traveler type bridge, the Rouen Transporter Bridge across the Seine.

By the late 1920, the bridge was not keeping up with demand. The upgrade began in 1929, adding lifting span with a automotive deck. The fix span across the top had to be raised to allow room for the lifted span, so the towers straight vertical sections were added. In addition, significant structure was added within the towers to accommodate the counterweights and lifting mechanism. The rebuilt bridge first lifted for a vessel 1930 Mar 29.

[Bridge Hunter Description]

So was the War Department afraid that the lift span would fall down?

LC-USF34-064038-D (b&w film neg.), cropped
Aerial bridge. Duluth, Minnesota

LC-USF34-064039-D (b&w film neg.)
Aerial bridge. Duluth, Minnesota
[Note that the ship has passed and the lift span is on its way down.]

LC-HS503- 705
Credit line: Photographs in the Carol M. Highsmith Archive, Library of Congress, Prints and Photographs Division.
Carol M. Highsmith's photographs are in the public domain.

Al Miller posted three photos with the comment:

Edgar B. Speer departs Duluth in late March 1984 as the first boat to leave port that spring. She's bound for Two Harbors to load taconite pellets. G-Tug Vermont will accompany the Speer to assist with icebreaking and docking.
I was working for the Duluth News-Tribune at the time and had just done a story previewing the shipping season -- always one of the most pleasant tasks of the year. The photographer assigned to shoot the first boat movement persuaded me to accompany him -- probably so he wouldn't have to write the two-sentence photo cutline himself. He knew the operators of the Aerial Bridge, so we were able to be on the span when they raised it to allow the Speer to pass. I don't remember why I had my camera with me that day, but I'm glad I did. I wasn't a big fan of the 1,000-footers but this turned out to be a series of photos I still treasure.

A view of the underside of the lift span.

Bjornberg Photography posted

Steaming by:

It was a blue bird kind of day late as I captured a close up of the Alpena's smokestack when she passed underneath the Duluth lift bridge late last year. Amazing to see an 80-year-old ship (the oldest operating on the Great Lakes) in such great condition!

2023 Calendar: tinyurl.com/ShipsontheGreatLakes23
Prints: BjornbergPhotography.smugmug.com

Because ship fans are normally after freighters in the harbor canal, this is the only photo I've seen with the span just part way up.

Rich Pedersen posted
The Federal Seto anchored in the lake as the Aerial Lift Bridge raises for a couple of sailboats this evening. 5/27/22
Chris Mazzella: Not uncommon
Lynn Theeck: It's been sitting there almost two days.

Michael Rainaldo posted four photos with the comment:

Not exactly ship related but then again, I guess it is. Enjoyed watching the MNDOT crews inspecting the Aerial Lift Bridge in Duluth, MN yesterday. Not often you get a close up look as they are usually hanging under the Blatnik or Bong bridges at 120 ft over the water, under the roadway & unseen to traffic overhead.
Interesting to watch was when a ship or boat came in & the bridge lifted as normal and the crew and equipment went up with it. I guess you just never know what you'll see on a morning bike ride.

Jeremiah Shoemaker: Ultrasonic and visual NDT! Love to see it!

Access the public interactive bridge map here: https://mndot.maps.arcgis.com/.../webappviewer/index.html...