Being Factual in an Alt History Story

I've been doing a lot of research for PATAPAN. I've nailed down most of what I needed (or what I didn't already have). I am taken aback by how many people are shocked that I would do research for an alternate history story. I'm changing the history as it's been taught to us. It's important that I get as many details as I can accurately so that readers can understand the points I'm changing are intentional changes and not just errors on the author's part.

Sure not everyone who reads it will be so into history that they know more about Benedict Arnold than he was a traitor and possibly at West Point. But it seems lazy to just write about history without keeping factual when I don't intentionally change things. A few train rides digging through Wikipedia refreshing what I already knew is enough to keep a novel set in the Missouri Territory ringing with honesty.

The story is set in the town of Arnold, Missouri just southwest of Saint Louis. The town is real (an exurb of the city) but was not founded at the time the story is set. I am writing a scene right now and the main character and his friends are crossing the river to Saint Louis. I'm curious how many people will think I've made a mistake or believe it's a change I've made for the story. Saint Louis at the time of the Louisiana Purchase was actually part of the Illinois Territory and not part of the Missouri Territory.



Here's a bit of history trivia for you. The Mississippi River didn't always flow the way you see it on a map today. The Army Corps of Engineers actually moved it, turning it from the west side of Saint Louis to the east side. If you ever go to Saint Louis and you hear about an area called Westport, you might be confused because there isn't any water nearby for a port. Well now you know. Saint Louis was the gateway to the west because leaving it crossed the Mississippi into the wild frontier (rather than being the first city you come to in the frontier as would be the case if it had been on the west side of the river).