Technically, Ohio is not the 17th state admitted to the United States. It is the 47th. During its 150th anniversary, government officials went looking for the records. As it turned out, there had been a small oversight. You see, while the constitution and boundaries had all been approved, Congress forgot to actually admit the state to the Union. Whoops. A resolution was introduced to admit Ohio as a state retroactive to March 1, 1803. Congress passed a joint resolution and Eisenhower signed it on August 7, 1953.

That's where the fun began. Tax evaders have claimed that since the 16th Amendment was introduced to Congress by the Taft administration, and Taft was born in Cincinnati, Ohio, that he was not a legal president (The Constitution explicitly states that presidents must be natural-born citizens of the U.S.). Hence, Taft could not legally introduce the 16th Amendment. Also of interest is that this line of reasoning would render the actions of presidents Harding, Hayes, McKinley, Garfield, Harrison, and Grant unconsitutional.

The argument against this is that the resolution in 1953 rendered all previous events legal, since Ohio was declared to have been a state since 1803.

The tax evaders have countered this by pointing out that the Constitution also says Congress can't make an ex post facto law. The question is whether retroactive admission of a state falls under this category (probably not). Not to mention everyone thought Ohio was a state for a century and a half. It's hard to fight 150 years of history in court.