Cascades to Coast

Why is Pluto not a planet?

Pluto was discovered in 1930 by Clyde Tombaugh in Arizona and is the only American to discover a planet in our solar system. At the time, the definition of planet was vague. The definition was formalized in 2006 buy the International Astronomical Union (IAU). To be a be a planet, a celestial body must:
1) Orbit the sun
2) Be round due to high gravity
3) Gravitationally dominate the region
Pluto's mass is only 0.07 times that of the mass of the other objects in its orbit, and was considered to not gravitationally dominate the region.
Basically, Pluto was considered to small compared to neighboring objects. As a result, Pluto was reclassified as a dwarf planet.