One other note - but the times machines came in the more "Modern" style, there weren't all that many US Mfg still in the game. And more and more went out of the picture as time when on - with some becoming only "Brand Names" no longer making their own machines.
At the time these machines were made, the major US players were National, White, New Home, Standard and Free.
SInger too -but since Singers are so easy to identify and they didn't put other names on their machines, they aren't really a concern. Wilcox & Gibbs too, but again you won't them.
Davis and Domestic went out around the 20's (I'm pretty sure, not going to look up dates right now)
in the 1895-1920 there were several more companies, and before that there were a LOT more companies making machines (they type that SteveH is after).
There are a lot of foreign companies, but I'm not trying to learn about them. My main area is top clamp US made machines around 1895-1940 era.