As with other parts of Michigan, the history of the eastern U.P. was defined by its Native American cultures, the 19th-century logging industry, and the Great Lakes’ use as a major shipping route. Names like Chippewa County, old logging towns like Blaney Park, and the presence of numerous lighthouses and shipwrecks along the Lake Michigan and Lake Superior shorelines are evidence of this diverse past.

Of course, the two main towns in the eastern U.P. have their own interesting histories. St. Ignace was founded by Father Marquette in 1671 and named for St. Ignatius of Loyola. Once the bustling hub of the 17th-century French fur trade, St. Ignace witnessed even more growth in the 1800s, as the logging and fishing industries prospered. Of course, the lumber industry came to an abrupt halt in the early 20th century, when the U.P.’s forests were nearly depleted of their timber. Although railroad ferries made it easier for travelers to cross the Straits of Mackinac from lower Michigan, it was the opening of the Mackinac Bridge in 1957 that improved the town’s fortunes, facilitating the flow of tourists.

Even older is Sault Ste. Marie, which was first settled by the Ojibwa Indians in the 1500s. After discovering a rich supply of whitefish in the turbulent waters, they established a permanent settlement along the shore. The Ojibwa lived here for more than 300 years, but the combination of warring Iroquois—forced west by European immigrants—and the ever-growing European settlement of Sault Ste. Marie (founded in 1668) eventually drove the Ojibwa from the region.

By the early 1800s, Michigan’s northern reaches were increasingly being settled, and people were discovering the bounty of natural resources—copper, iron, lumber, grain—ringing the shores of Lake Superior. The only problem was those rapids. For decades, ship cargo had to be unloaded by hand, portaged around the rapids by horses and mules pulling carts, then reloaded onto another boat. In 1839, the American Fur Company built a short railroad line, which eased the job, but it remained backbreaking and exceedingly slow. While shipping was booming on the lower Great Lakes, Superior remained largely isolated, its cargo backed up by the rapids.

Eastern industrialists began lobbying for government-funded locks. Locals, however, opposed such a project, fearing the loss of their portaging business. The town managed to stave off the inevitable until 1852, when President Millard Fillmore signed a bill authorizing the first lock at Sault Ste. Marie. In 1855, the State Lock opened, a system of two 350-feet-long locks. In the first year, nearly 12,000 tons of iron ore passed through the locks; within a decade, that figure grew to more than 120,000 tons. By World War I, the nation’s hunger for iron and copper, coupled with the opening of vast iron mines in Minnesota’s Mesabi Range, made the Soo Locks the busiest shipping canal in the world.

Soon after the completion of the State Lock, the burgeoning commercial traffic indicated that more locks were needed. The 515-foot Weitzel Lock opened in 1881. Since then, a succession of locks have been built, both to handle the traffic and the increasing size of Great Lakes–area ships. Today, three U.S. locks are in operation (there’s a fourth smaller lock on the Canadian side), including the 1,200-foot Poe Lock built in 1968 to accommodate the huge vessels now common on the Great Lakes.

Today, Sault Ste. Marie is inseparable from the locks that shaped its past. Although Lake Superior State University and the Ojibwa-owned Kewadin Casino are two of the area’s largest employers, tourism remains a staple of the economy—with many of those visitors coming specifically to see the parade of commerce that incessantly passes through town.