The 45-70 round is well into its second century of existence with a history dating back to its introduction by the U.S. Army's Springfield Armory in 1873 as the Springfield Model 1873. Its full technical name is the .45-70-405: the ".45" is the bullet diameter (11.6 mm), the "70" is the weight in grains of the black powder, and the "405" is the weight of the lead bullet (another offering included a .45-70-500 as well). During the last decades of the 19th century, the .45-70 held great sway as one of America's important big game rounds.
The popularity of the .45-70 Govt. declined as the 20th century dawned so you won't find as much commercially produced ammo for sale as you once would have. Winchester stopped production of .45-70 chambered rifles in 1935. Interest was revived in 1972 when Marlin begin production of its "new" Model 1895 lever action gun chambered in .45-70 caliber; the round has seen a modest increase in use, especially in the U.S., Australia, and New Zealand. The large diameter bullet punches a big hole in whatever it hits; however, slower velocities and longer distances may not always produce the necessary hydrostatic shock for clean, quick kills. Although some advocate the .45-70 Govt. ammo for use on dangerous game, its successful use may critically (read "life and death" important) depend on the skill of the shooter's cool-headedness in dangerous situation!