Earth Ponies are a race of pony that has neither wings nor horns, and thus do not exercise any overt magical ability. Instead, earth ponies generally exhibit more stamina, fortitude, and durability than the other two races. Their inherent magical ability involves an underlying connection to the earth and the environment, one that is passive and less overt than other forms of magic. Their lack of magical ability also drives them to seek more innovative solutions to their problems, generally making them more industrious and inventive.
Before the War
While at a disadvantage, earth ponies would be found in most industries and professions occupied by unicorns and pegasi, with the obvious exception being those involving flight.
Due to their inherent connection of nature, only earth ponies can grow food, and thus are as responsible for the well-being of Equestria as the unicorns and pegasi.
During the War
Earth ponies were quick to establish themselves as the most industrious and adaptable of the three species. Applejack had founded the Ministry of Wartime Technology, and with the assistance of the Ministry of Arcane Sciences would go on to build a suit of power armor for earth ponies. Wearers of this power armor were known as Steel Rangers. The majority of weapons and robotics development was headed by earth ponies. Earth ponies were also known for their cunning, most apparently in the tasks undertaken by the Ministry of Morale.
After the War
Much like unicorns, earth ponies have reverted to their pre-war responsibilities for the most part. Earth ponies pull trains, bake, and act as merchants among other things. Steel Rangers continue to band together, treating anyone without power armor as annoyances at best, obstacles at worst.
Notes and Trivia
Although Pinkie Pie is an Earth Pony, she possesses a special form of magic unseen in any other pony. It is not known if there were any other earth ponies with unusual magical talents as well.