“When you look at 12th Street Beach on Google Earth, there’s a dark line stretching between the planetarium and southern end of the beach. People on Facebook say it is submerged railway tracks but I think it’s a submerged breakwater. What is it?
“This is indeed a submerged seawall, also known as a submerged bulkhead.
“The 12th Street Beach is nestled in a sort of bay at the northern end of Northerly Island – just south of the Adler Planetarium. And out there in the water, below the surface, the seawall encloses the bay.
“You can totally see why some might think these are submerged railroad tracks. In fact, the Illinois Central Railroad does run up the lakefront – but it never came this far out.
“The 12th Street Beach isn’t the only artificial thing on Northerly Island. It’s actually man-made.
“Northerly Island is so named because it was the northernmost of a string of artificial lakefront islands architect Daniel Burnham proposed in his ambitious 1909 “Plan of Chicago.” It was the only one actually built.
“In the late 1920s, several women’s organizations advocated for the construction of a bathing beach on the island, which became the 12th Street Beach.
“The Adler Planetarium opened in 1930, and in 1933 and 1934, the island and nearby Burnham Park hosted “A Century of Progress,” the second World’s Fair to be held in Chicago.
“The island’s longest chapter is, of course, as Meigs Field, Chicago’s one time “third airport”. After its lease expired, it was famously closed – in fact bulldozed – in a late night raid ordered by Mayor Richard M. Daley in 2003.
“Today, Northerly Island is home to a concert venue and nature preserve, closed now due to COVID-19. But of course the beach and seawall remain – with or without any swimmers.” (WTTW Chicago, 9/12/20)
Watch the full video at WTTW Chicago
Ask Geoffrey: Seawall or Railway Tracks?, Quinn Myers, WTTW Chicago, 9/17/20