Pushing the Limits

 

Geographical facts tend (I find) to lodge quite firmly in one's mind after one teaches them to students. I've taught Native American history for nearly 25 years now, and in my lectures have usually stated that the northern growing limit of maize is the latitude of southern Ontario. This supposed geographic fact, I would go on to say, gave the Wendat nation, who originated in southwestern Ontario, a considerable commercial advantage: they could produce a large surplus of corn, then trade it to northern neighbors who could not grow the crop. I probably read this in grad school, in a book or article by an early American historian, and kept it in memory for the next two decades.

Ojibwa village, Sault Ste. Marie, 1846 - via Wikimedia Commons

 

It's now pretty clear that I was wrong about that. Monographs by Cary Miller (Ogimaag, 2010) and Brenda Child (Holding Our World Together, 2012) observed that the Minnesota Ojibwas could grow maize in raised-bed fields, at a latitude above that of the Wendat homeland. I didn't understand the mechanics of this form of cultivation, and assumed it was probably conducted on a small scale. Clearly I was wrong about this. A new LIDAR study of the Sixty Islands site near Michigan's Upper Peninsula, conducted by Madeleine McLeester, has revealed that the Menominees and their predecessors were raising corn on a large scale from approximately 1000 to 1600 CE. The techniques they used to farm in this marginal environment included field drainage, intensive use of compost, and the aforementioned raised beds, which kept a temperature a few degrees higher than that of the underlying topsoil. These sophisticated horticultural practices allowed the region's farmers to raise corn on a very large scale - approximately 300 hectares, in the case of Sixty Islands.

 

In future courses I plan to share these findings (as well as the earlier work of Child and Miller) with students. I'll add that when they want to raise a valuable crop, human beings often find a way to push the apparent natural limits on its cultivation. This was true of Menominee and Ojibwa women during the Little Ice Age; it was also the case with Euro-American farmers in Vincennes in the late 1700s. I've mentioned to students, and to any other hapless person I could trap in a conversational cul-de-sac, that the northern limit of cotton cultivation in the United States is just below the latitude of Cairo, Illinois; I've seen cotton fields in the Missouri "Bootheel" and Kentucky's Jackson Purchase district, but not any further north. During the first American cotton boom, however, white settlers in southern Indiana were happy to experiment with the crop, even though it requires 180 frost-free days to grow and one cannot be assured of them north of the Ohio River. Constantin Volney observed that white farmers in Vincennes raised cotton and tobacco, and suggested that the local climate was warm enough for both crops - the Wabash River moderated local temperatures in early spring and late fall (Harlow Lindley, ed., Indiana As Seen by Early Travelers [Indianapolis, 1916], 18-19). I suspect, though, that the Vincennes habitants could not reliably raise a large crop of the desirable fiber, and it eventually became cheaper to specialize in wheat or tobacco and buy cotton textiles elsewhere.