I don't know the specifics of the St. Louis canoes, but most 20th century wood-canvas canoes have cane-filled seats except for those built during a WWII cane-shortage. I know Old Town used a slatted seat from about 1943-'47, and Penn Yan filled the opening in their seats that otherwise would have been cane-filled with a hunk of plywood. Some folks with these war-era canoes change the seats for those with cane, because cane is lighter weight and more comfortable... good-looking too... adds a bit more design and a different texture to the canoe. Chances are that your canoe had cane seats, and even if not, it would be your choice to go that way if you wanted to.
Someone with a canoe like yours should be able to post pictures so you can copy the seat-design (wooden part-- rails and stiles). My guess is that the caning would have been the traditional 7-step (like a dining room chair), but some companies and some individuals preferred the "canoe weave" that cuts out a step and has a springier feel. There are threads here about caning-- setting things up, etc.-- and there are YouTube videos in addition to instruction in books. But ask questions here, too. We like progress reports and pictures!
Kathy