Live vessel activity, navigation season status, and the visitor guide to the lock complex at Sault Ste. Marie, Michigan
The Soo Locks at Sault Ste. Marie, Michigan are the busiest commercial lock system in the world by tonnage. Roughly 75 percent of all United States iron ore moves through here on its way from the Minnesota and Wisconsin head-of-lakes ports to the steel mills of Lower Lake Michigan, Lake Erie, and the Detroit River. The locks lift vessels 21 feet between Lake Superior and the lower Great Lakes, bypassing the rapids of the St. Marys River. The system is operated by the U.S. Army Corps of Engineers, Detroit District, and is open to the public during the navigation season.
This page is a live tool. The status indicator above is calculated from the official Soo Locks operating calendar. The vessel map below shows real-time AIS positions of ships in the immediate lock area. Below the live data is the visitor guide: lock dimensions, the new Poe-replacement lock, how to watch a vessel transit, and what each ship category looks like when it comes through.
Real-time AIS positions of vessels currently within the lock complex and the St. Marys River approach channels. Ships transiting downbound from Lake Superior approach from the upper right; upbound traffic from Lake Huron approaches from the lower right.
For named vessel schedules and full lock transit listings, the daily Great Lakes Gazette publishes morning summaries during the navigation season. The Gazette tracks the same AIS feed shown above plus port reports across all five Great Lakes.
Two locks are currently operating: the Poe Lock and the MacArthur Lock. The Poe is the only lock at the Soo that can handle vessels larger than 730 feet. Every 1,000-foot laker in the U.S. fleet (the Paul R. Tregurtha, Edwin H. Gott, Edgar B. Speer, Burns Harbor, Stewart J. Cort, Indiana Harbor, and a handful of others) is dependent on the Poe to move between Lake Superior and the lower lakes. If the Poe ever goes down for an extended unplanned outage, the result would be a near-total disruption of U.S. steelmaking iron ore supply.
That single-point-of-failure problem is the reason for the new lock currently under construction on the site of the decommissioned Davis and Sabin Locks. The replacement, often called the New Poe or simply the New Lock at the Soo, will match the Poe's 1,200-foot length and 110-foot width, providing redundancy for the 1,000-footers. Construction began in 2020. The U.S. Army Corps of Engineers projects an operational date in the mid-2030s.
The Soo Locks close annually from mid-January through late March for ice conditions and scheduled maintenance. The exact close and reopen dates vary slightly year to year and are set by the U.S. Army Corps of Engineers. During the close period, no vessels transit; American and Canadian icebreakers (the USCGC Mackinaw and CCGS Samuel Risley) work to keep the surrounding lake and channel ice managed for the reopening. The Canadian Sault Ste. Marie Canal, a smaller pleasure-craft lock on the Canadian side, operates only seasonally and serves recreational traffic.
Ships transiting the Soo fall into a few recognizable categories. Once you have seen one of each, you can tell them apart from a distance.
The thirteen U.S.-flagged 1,000-foot lakers are the largest vessels on the Great Lakes. They run iron ore, coal, and limestone in lake-only service and never leave the system. They are the most photogenic vessels at the Soo. The Paul R. Tregurtha is the longest at 1,013 feet 6 inches. The Edwin H. Gott, the Edgar B. Speer, and the Burns Harbor are also commonly seen at the Poe. Only the Poe Lock can hold them.
Oceangoing vessels that have transited the St. Lawrence Seaway from the Atlantic to reach the upper lakes. Salties are typically 600 to 740 feet long, limited by Seaway lock dimensions. They carry mixed cargoes (steel coils, grain, project cargo). Their hulls show ocean wear and salt staining. They often fly foreign flags. At the Soo they handle through both the MacArthur and Poe.
Vessels of the Canadian Algoma Central or CSL fleets. Typically 740 feet, slightly older designs, white or gray paint. They run grain from Thunder Bay, salt from Goderich, and iron ore from Quebec ports. They can transit either lock.
The American Steamship Company, Interlake, and Great Lakes Fleet vessels in the 600 to 730-foot range. These are the original post-Edmund Fitzgerald generation of bulk carriers. Both lock options available.
A pusher tug locked into a barge notch, operating as an integrated unit. Increasingly common in the U.S. fleet as a more economical alternative to traditional self-unloaders.
Lake Superior cruise traffic has grown since 2019. The Ponant Le Champlain, Viking Octantis, Pearl Mist, and other small luxury vessels transit the Soo during the summer cruise season, typically May through October.
The Soo Locks Visitor Center is on Portage Avenue in downtown Sault Ste. Marie, Michigan, immediately adjacent to the MacArthur Lock. The viewing platform sits about 25 feet above the lock chamber and provides an excellent vantage for watching vessels enter, lock through, and depart. Admission is free.
The Visitor Center is open daily during the navigation season (typically late April through October), 9 a.m. to 9 p.m. during peak summer months, with shorter hours in spring and fall. The viewing platforms are accessible 24 hours a day during the navigation season; the indoor exhibits and gift shop have set hours.
The most reliable way to see a 1,000-footer transit is to check the daily vessel schedule the morning of your visit. The USACE publishes the day's planned lock transits at the Visitor Center; the schedule is also available informally through the Boatnerd community network and reflected in the AIS map above. Plan for 90 minutes to 2 hours at the Locks: 30 to 45 minutes for the actual transit, plus time for the Visitor Center exhibits and the engineer's overview film.
Peak vessel traffic runs from late spring through late fall. July and August offer the most consistent weather and the most daylight, but September and October bring fall color along the St. Marys River and slightly less crowding. The shoulder season at season open (late March / early April) and close (early January) offers spectacular ice-vessel photography but unpredictable weather.
The Canadian Sault Ste. Marie also offers vessel viewing at Roberta Bondar Park and the Bondar Pavilion. The viewing angle is different (closer to the ship channel) and there are typically fewer visitors. The two Saults are connected by the International Bridge. The Sault Ste. Marie Michigan stop card on the Circle Tour guide and the Sault Ste. Marie Ontario stop card both have additional visitor notes.
Can you watch a 1,000-footer go through the locks?
Yes. The Poe Lock handles all 1,000-foot vessels, and the Visitor Center viewing platform is immediately adjacent. The best time is during the morning or afternoon traffic peaks. Check the daily vessel schedule or the AIS map above to time your arrival.
Is there a fee to use the locks?
No. The Soo Locks are operated by the U.S. Army Corps of Engineers and are toll-free. Commercial vessels do not pay a transit fee, unlike the Panama Canal or Suez Canal. The locks are funded as part of federal navigation infrastructure.
When does the new lock open?
The new replacement lock (which will match the Poe in size) is under construction on the site of the decommissioned Davis and Sabin Locks. USACE projects an operational date in the mid-2030s. Construction began in 2020.
Why does the lock close from January to March?
Ice. The St. Marys River and the eastern end of Lake Superior freeze over during the winter, and operating the locks through pack ice damages the gates and structures. The shutdown is also used for major scheduled maintenance, dewatering inspections, and repairs that cannot be done while vessels are transiting.
What is the most-transited vessel at the Soo?
The 1,013-foot Paul R. Tregurtha makes the most transits annually, running iron ore, coal, and limestone year-round during the navigation season. The Edwin H. Gott and Edgar B. Speer also rank among the highest-frequency transits.
Can pleasure craft use the locks?
Yes. Pleasure craft use the smaller Canadian Sault Ste. Marie Canal lock on the Canadian side (not operated by USACE). The U.S. locks handle commercial vessels and occasional government and special-use traffic; pleasure craft are not typically routed through the Poe or MacArthur.
How can I get notified when specific ships are transiting?
The Great Lakes Gazette daily brief mentions notable vessel movements at the Soo. MarineTraffic offers paid vessel tracking with email alerts. The Boatnerd "Calumet River Reporter" and similar AIS-driven Discord and Twitter feeds also push notifications for specific ship arrivals.