Fun fact: St. Anthony Falls is the only waterfall along the 2,300 miles of the Mississippi River.
Not-so-fun fact: The Upper St. Anthony Falls Lock and Dam opened in 1963, and on Tuesday night, the lock will close for good.
A Minneapolis treasure
Lock master Mike DeRusha knows the gates like an old friend, the sounds of rushing water and blaring horns just another reminder he's home.
"In my opinion, it is one of Minneapolis' treasures because it's right in the heart of downtown and you look around and it's like we are in a goldfish bowl," he said.
It's the carp
Why the closure? Invasive carp are to blame. They've been using the lock as a pathway, and per the Water Resources Reform and Development Act of 2014, it has to be shut down to stop them.
"Not later than 1 year after the date of enactment of this Act, the Secretary shall close the Upper St. Anthony Falls Lock and Dam," the act reads, dated June 10, 2014.
The act doesn't actually say carp are the culprits, but U.S. Sen. Amy Klobuchar and U.S. Rep. Keith Ellison have championed its closure.
"With our environment and economy at stake, Minnesota must win the battle to keep invasive carp out of our waterways," Sen. Klobuchar said last May. "We need to do everything we can to stop the further spread of this invasive species and closing this lock represents an important step in that fight."
Also known as Asian carp, they can wipe out a healthy lake because they are capable of eating between 20 and 120 percent of their body weight each day, out-competing the native fish populations.