Robert Mazrim is haunted by a highway that no longer exists. Tantalizing bits of evidence that it served travelers for thousands of years keep disrupting his regular work as a historical archaeologist. Even the interstates he drives between Saint Louis and Peoria appear to follow the same ghostly corridor, a mile or two wide, through which the old road ran.

Despite his reluctance to pursue the topic, Mazrim is now drafting a publication that will lay out the circumstantial evidence–none of it conclusive–that Native Americans were using this corridor on a regular basis as early as 1200 BC. In August his archaeological museum in Elkhart, called Under the Prairie, will, in conjunction with the local historical society, offer wagon rides that show off the distinctive natural and cultural history of Elkhart Hill–including the two flat spots that are probably among the last visible traces of the old road.

Today most travelers along these lines take Interstate 55 as far as Lincoln and then swing north on Interstate 155. People of a certain age know I-55 as a revised and improved version of Route 66, and I-155 as a revised and improved version of Illinois 121. Those who take an interest in Illinois history may also know that these old highways follow the corridor of the still older Edwards’ Trace. The question that’s bedeviling Mazrim and some colleagues is this: did Edwards’ Trace follow a much older prehistoric trail?

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In fact, the cycle of terror continued up and down the trace for years to come. In 1814 Kickapoo raiders went as far south as Wood River, killing members of the Reagan and Moore families. “Settlers pursued this band up the Indian Trail to the headwaters of Sugar Creek,” writes John Mack Faragher in Sugar Creek: Life on the Illinois Prairie, “where they killed one warrior in the timber and recovered Mrs. Reagan’s scalp from his pouch.”

Instead they followed existing trails, Edwards’ Trace being the main one. And along those trails, their settlements clustered at the far northern edge of the area being surveyed by the government at the time. For reasons that aren’t yet known, they skipped what look like equally desirable places along the way. One of these settlements was on Edwards’ Trace, along Sugar Creek near Springfield. Comparable places farther from known trails, such as Decatur, weren’t settled until later. “People in Kentucky heard about the Sangamo Country,” says Mazrim. “They picked this over comparable places east of here. That has a lot to do with why the state capital is here.”

In 1821 Elijah Iles built and stocked a store two miles west of the trace, in what became Springfield. His stock came from Saint Louis by water to Beardstown, not up the trace. The only store for miles, according to Mazrim, it pulled the trail west.