Empire City is a Human settlement along the coastal side of the Empire State.
It is briefly referenced in a single episode, which Sardonyx had a coffe cup that read "I love EC" with a heart symbol on it.
Empire City is mentioned during a fake "United Emergency Signal" as being one of the three cities to be called to evacuate inland due to an oncoming Hurricane.
Empire City officially debuted when Greg, Jasper, Rarity, Steven, Peridot, Pinkie, Jade, Bismuth, and Lapis went there after Greg got 10,000,000 dollars in a checked for copyright claims over Marty's use of his song.
My Little Universe II
Empire City became the main target for Grogar to first attack on earth with many of his ships and weapons. When that failed though, he called Sumu to the area, and it became the first spot part of Sumu's invasion on Earth. While it is somewhat repaired when it was over, it still was left badly damaged by the end of the finale.