Answer: New Mexico

As far as most of the world is concerned, poor Pluto got downgraded from planet to dwarf planet (or planetoid) back in 2006 when the International Astronomical Union revised their definition of what constitutes a planet. For the curious, Pluto was downgraded because it lacks enough gravitational pull to distinguish itself from other dwarf planets in similar nearby orbits.

Whatever the reason was for the change in Pluto’s classification, New Mexico’s House of Representatives was having none of it. For you see, the man who discovered Pluto back in the 1930s, Clyde Tombaugh, was a long-time resident and a former professor of astronomy at New Mexico State University. Regardless of what the international astronomy community had to say about the matter, the people of New Mexico had a very strong opinion about the matter.

In 2007, the House of Representatives passed a resolution declaring that March 13, 2007 would be observed as Pluto Planet Day and that whenever Pluto is in such a position that it can be observed in New Mexico’s night skies it is, in fact, still a full-fledged planet.

Bonus Trivia: Because Clyde Tombaugh was born in Illinois, the Illinois State Senate passed a resolution in 2009 that asserted Pluto was “unfairly downgraded to a dwarf planet” by the IAU.