Pluto wasn't the first dwarf planet, but it was the first object discovered that was later reclassified as a dwarf planet.

Here's why:

* The concept of dwarf planets didn't exist until 2006. The International Astronomical Union (IAU) defined the term "dwarf planet" in 2006.

* Pluto was discovered in 1930. For decades, it was considered the ninth planet in our solar system.

* Ceres was discovered in 1801. However, it was initially classified as an asteroid, not a planet. Later, it was reclassified as a dwarf planet, based on the 2006 IAU definition.

Therefore, while Ceres was the first object in our solar system to be later reclassified as a dwarf planet, Pluto was the first object to be discovered that is now classified as a dwarf planet.