The waterway was dredged in the 1860s, extending a small river previously used by natives for transportation and fishing. The effort was a joint venture between the United States government and several mining corporations. Legislation for construction of the canal was passed in 1861. This legislation created the Portage Lake & Lake Superior Canal Co. The company began construction of the canal in September 1868. The canal starts at the mouth of Boston Creek and continues on to
Lake Superior. The expanded canal allowed freighters to haul
copper from the rich copper mines of the
Keweenaw Peninsula out through
Lake Superior to larger cities. It also enabled supply boats and freighters to reach the cities of
Houghton and
Hancock, which supplied goods to most of Michigan's copper region. The expanded canal and shipping lane has a depth of , deeper in some locations. As the waterway connects Lake Superior to itself, there are no locks needed. The local mines'
stamp mills dumped large quantities of
stamp sand (containing traces of copper and chemical leaching agents) into the waterway, causing significant environmental damage near the sand dumps. Stamp mills on the waterway included the
Old Atlantic, old
Quincy,
Pewabic, old Franklin, and the
Isle Royale mills. The area north of the waterway is known locally as
Copper Island, because the waterway separates the northern part of the Keweenaw Peninsula from the mainland. The only land route across the waterway is
US 41/
M-26 across the
Portage Lake Lift Bridge. ==Tourism==