The Lonely Mountain. Erebor was first settled just after Moria
was deserted, and later attracted the attention of Smaug, who until
the Quest to destroy Smaug was successful in the year 2941 of the
Third Age. After this Erebor thrived and continued to grow. There
is no record of what end it finally came to, if any, Erebor may
still be in existence.
The Lord of the Rings