Ceres was considered a planet in the first half of the 1800's, along with a bunch of things in the asteroid belt. There was a point where there were 64 planets.

In the present state of knowledge astronomers give us the following list:
Sixty-four "primary planets" revolving round the Sun as our Earth does.
Twenty satellites, including our Moon.
Of the sixty-four primary planets fifty-six are asteroids, comparatively small bodies, all of which were discovered in this century, and fifty-two since the year 1844.]