the only dumps I've found were at small farms which had been abandoned by now and grown in with tree's , I've never like found an actual town dump , there is semi modern now closed maybe 50 era dumps outside of both Huntsville and bracebridge but I doubt the town would ever allow someone to dig them up . as to where the original 19th centrury dumps would be ? is a mystery , back at the turn of the century all the tree's here were cut down and logged so an area that might of been empty back then could now be fully forested or a swamp/wetland type area
Old pics can be really deceptive when it comes to dumps, I've never seen an old picture which clearly shows a dump. Dumps don't really look like anything in old pictures, they just look the same as dirt from far away. But a farm does suggest that there probably wasn't a major dump there. I'm thinking the rail yards are even more likely then. Rail yards very frequently had dumps under them because there wasn't much else you could do with the land since you couldn't build on it.
If you ever have some spare days with nothing to do, I can almost guarantee that you can find information about where the dumps are in the pre-1920 newspapers. It'll just take a really long time, but it could be worth it. Or you might find out it's in an area you aren't allowed to dig and it'll be a waste of time. It can go either way. I wouldn't expect you to find anything in the history books, no one other than bottle collectors cares about old dumps.
One way to narrow down locations is to remember that when dumping trash, they didn't like to make trash mountains like they do now. So they generally only dumped in low-lying areas which could be made flat. This means into rivers, swamps, quarries, or any other low-lying area. If you're walking around checking places out, you can also more or less cross a place off if you see bedrock sticking up through the dirt. Since your area appears to have a lot of rocks, that should be helpful in eliminating spots.