The Mississippi River starts its 2,340 mi (3,770 km) journey to the Gulf of Mexico at the lake. Henry Schoolcraft identified Lake Itasca as the river's source in 1832. He had been part of a previous expedition in 1820 led by General Lewis Cass that had named nearby Cass Lake (which is downstream from Itasca) as the source of the river. The Ojibwe name for "Lake Itasca" was Omashkoozo-zaaga'igan (Elk Lake); this was changed by Schoolcraft to "Itasca" ,., coined from a combination of the Latin words veritas ("truth") and caput ("head"). It is one of several examples of pseudo-Indian place names created by Schoolcraft.
The channel of the Mississippi as it emerges from the lake was actually moved in the 1930s by the Civilian Conservation Corps, as part of project to create a more pleasant experience for visitors. The project included the draining of the surrounding swamp, the digging of a new channel, and the installation of a man-made rock rapids. Wading across the rapids in bare feet – walking across the Mississippi River – is a popular recreational activity for summer tourists.
The western arm of the lake is fed by two small streams on its south end. Nicolett Creek, which is considered too small to be considered as the headwaters, starts in a nearby spring. Another small stream leads into Itasca from Elk Lake, which in turn is fed by two other streams. In 1887 Williard Glazier promoted a campaign to consider Elk Lake, which he called Glazier Lake, as the true source of the Mississippi. These streams, however, are generally considered too small to be categorized as the headwaters of the river.
The decision was made by Jacob V. Brower, a land surveyor and president of the Minnesota Historical Society, who after spending five months exploring the lakes ruled that the lakes and streams further south of Lake Itasca were not the true source of the Mississippi. Brower was to campaign aggressively to save the lake from logging. On April 21, 1891, the Minnesota Legislature officially made it a state park by a margin of one vote. Brower is now called the "Father of Lake Itasca" and the visitor center is named in his honor.