What state is most similar to Ontario?

[King of Kensington]

On a technical basis, Illinois might seem like it would work but nothing in Illinois really resembles Canada (downstate Illinois would be "sui generis" in Canada). New York would work if it wasn't for the fact that NYC is arguably the world's most important city. Michigan is, quite literally, like Ontario though. Culturally speaking, these two places are siblings! I wouldn't over think the Toronto-Detroit analogy tbh.

Illinois is in the heart of the Corn Belt (a fully American region) and Chicago dominates Illinois in a way Toronto doesn't in Ontario.  Michigan does share a lot of geographic similarities with Ontario: the centrality of the Great Lakes and a "Northwoods" type region.    

Ontario shares some cultural similarities with the "Lakes states" of Michigan, Wisconsin and Minnesota.

[King of Kensington]

Not a huge bearing on anything, but Toronto sports teams (Raptors and Blue Jays) play in eastern divisions with New York and Boston, rather than in the central divisions with Chicago and Detroit.

[Hatman 🍁]

Toronto is very much like a mini-New York. It's their respective country's largest cities, and they're both home to large diverse, cosmopolitan populations.

[Sol]

I think there's actually a decent argument to be made that DC in some ways is the US city most similar to Toronto, in that both are 'rising cities' as DFB put it, but also have actually large pre-car urban cores.

SF is the only other US city I can think of where that's true, but obviously there are stark differences there which don't really obtain for DC-Toronto (Silicon Valley, SF is arguably more important on the world stage than either).

[King of Kensington]

I think there's actually a decent argument to be made that DC in some ways is the US city most similar to Toronto, in that both are 'rising cities' as DFB put it, but also have actually large pre-car urban cores.

That is a good analogy.  DC and Toronto had similar postwar growth trajectories.  Both were "second tier" (i.e. top 15) metropolitan areas of around 900,000 in 1940 and have similar populations today.  

And DC suburbs are more "sunbelt" like as they are largely post-1980 compared to other cities in the BosWash corridor.  The "905" region surrounding Toronto is also rather "sunbelt" like in typology.

[If my soul was made of stone]

I haven't spent much time in Ontario myself, but in light of my particular set of experiences I was most reminded of Pennsylvania.

-One major urban corridor with satellites (Golden Horseshoe / Philadelphia + Lehigh Valley) and one smaller metro near a border (Ottawa / Pittsburgh)
-Diverse major cities, mostly very white elsewhere
-Rust Belt trappings
-Strong regional identities

[King of Kensington]

A lot of the older parts of Toronto and Hamilton look like this:

https://tinyurl.com/45dzn3rj

[King of Kensington]

Michigan had an Ontario imprint.  It had the second largest number of Canadian-born in 1930 (after Massachusetts), and Canadians were the largest foreign-born group in the state.  But obviously they've diverged significantly since.

[King of Kensington]

Geographically Ontario lines up quite well the Great Lakes basin/region:

https://project.geo.msu.edu/geogmich/michigan/Maps_Graphics/Watershed.pdf