How many US states' names begin with the letter "O"?

There are 3 states that start with O. The 3 states that start with O are: Ohio, Oklahoma, and Oregon. Ohio sits in the US Midwest, linking the country's Northeast to the Midwest. The southern central state of Oklahoma is the 20th largest in the US by area and was the 46th to enter the Union. The northwestern state of Oregon is the 9th largest in the US in terms of land area, but it has a sparsely spread population by comparison.

Source: World Population Review