M99 was discovered on March 15, 1781 by Messier's colleague and friend, Pierre Méchain.  Charles Messier measured its position and included it in his catalog on April 13, 1781, immediately before finishing the third and final published edition.

M99, although situated in constellation Coma Berenices, is one of the bright spiral members of the Virgo Cluster of galaxies.  It is of type Sc and is unusually asymmetric.   The nucleus is shifted to the upper end of my picture.  It is speculated that this asymmetry could be due to semi-recent encounter with other members of the Virgo Cluster.  This hypothesis may be seconded by the fact that its recession velocity of 2324 km/sec is quite high for a Virgo Cluster member.  This is the highest recession velocity measured for a Messier galaxy (and thus a Messier object at all).  This means that M99 is moving away from us through the Virgo Cluster with a high proper (or peculiar) velocity of approximately 1200 km/sec.

¹http://www.seds.org/messier/m/m099.html