27: Arizona, California, Colorado, Connecticut, Florida, Georgia, Idaho, Illinois, Iowa, Louisiana, Minnesota, Missouri, Montana, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Rhode Island, South Carolina, South Dakota, Vermont, Washington, Wisconsin, and Wyoming.
Related Q&A：
How many states in the US begin with o？-Well, let me think for a sec. Hmm... As far as I know, there aren't that many states in the US that begin with the letter \O\ Off the top of my head, I can only think of Ohio. So, the answer is just one. That's it! I'm pretty sure there aren't any others. But you know, it's always good to double-check just to be sure.
