This object was observed by Pierre Méchain on March 12, 1781, and by Charles Messier on March 24, 1781, together with M108 when he measured M97. William Herschel has found this galaxy independently on April 12, 1789, and cataloged it as H IV.61 (incorrectly misclassifying it as a planetary nebula).

M109 is about 7-by-4 arc minutes in angular extent, and of apparent visual magnitude 9.5 or 9.6. Visually, only its bright central region together with the bar can be seen, and appear pear-shaped in smaller telescopes.
M109 is about 55 million light years distant, as it is receding at 1142 km/sec, and a member of the Ursa Major Cloud, a giant but loose agglomeration of galaxies. Tully took individual distances from the redshift in a model taking the Virgo-centric flow into account. The distance of this galaxy, however, may be a bit smaller, as the average recession in this cloud is lower, and some part of the surplus may be peculiar velocity.

The type I supernova 1956A occured in this galaxy on March 17, 1956, and reached 12.8 mag (or up to 12.3, according to some sources) in its maximum.