Discovered by Johann Elert Bode in 1774.
M81, also known as Bode's Galaxy, is located in the constellation of Ursa Major and is approximately 12 million light years distant. It is relatively bright with a total visual magnitude of 6.8 and can be viewed easily with most amateur telescopes. M81 is a large spiral galaxy and is the dominant galaxy of the M81 group. M82 is a smaller galaxy located only about 150 thousand light years from M81. In the relatively recent past, in astronomical terms, the two interacted gravitationally as they passed in close proximity. M82 apparently was the "loser" in this encounter and was disrupted to a greater extent by M81's much larger gravitational mass.
1http://www.messier.seds.org/m/m081.html