Automatic counters at the Lake Superior Maritime Visitor Center in Canal Park logged their 20 millionth guest last week, the center said in a news release Friday.

Often called "the marine museum" and located at the foot of the Aerial Lift Bridge, the visitor center is free and was among the first tourist attractions in the city of Duluth. It has faced every sunrise, every squall and every visiting ship since 1973. It receives more than 400,000 visitors annually.

The name of the 20 millionth visitor is not known, only that the figure was tripped by yet another guest across the center's 46 years of operation. It is cooperatively owned and operated by the 700-member Lake Superior Marine Museum Association and the U.S. Army Corps of Engineers.

"In a lot of cases people just stumble upon it and are surprised about what we have to offer," interim director Sara Summers-Luedtke said in the news release.

The visitor center has evolved through the years. New this year: an interactive Soo Locks exhibit, and an updated Edmund Fitzgerald exhibit that focuses on images of the crew and features video of the freighter during its heyday; it sank in 1975 with a crew of 29 people. Another new exhibit at the entryway to the center shows real-time rip current conditions at Park Point and explains the dangerous phenomenon. Coming later this year: an interactive vessel-tracking and harbor exhibit, with real-time video of Two Harbors' ore docks and the Wisconsin Point entry in Superior.

The visitor center is open 10 a.m. to 9 p.m. through Labor Day, then 10 a.m. to 6 p.m. until spring.