Well, gunga, the .44 Magnum was introduced in the early 1950s, first as a custom handload then developed as a commercial response to hand-load soup-ups of the .44 Special and .45-70 Springfield and the .45 Long Colt, cartridges which had been around since shortly after the turn of the 20th Century for the former and the 1880s for the latter 2. One of the more influential proponents of the .44 Mag round was the late outdoorsman and writer Elmer Keith (who also was hugely instrumental in the success of the .357 Mag), though hot-loading long had been a popular subject in gun p[ublications worldwide. Thanks largely to Keith's efforts, both Smith & Wesson and Remington began commercial support for the .44 Mag round, in 1955. Smith & Wesson in 1956 introduced the now legendary Model 29, chambered specifically for the new Remington-made cartridge, with Sturm, Ruger beating them to market by a few months with the also legendary "Flattop" Blackhawk. Both revolvers were immediate runaway successes, selling in far greater quantity than either manufacturor had anticipated - something which disrupted other production plans for a couple years. This year, Sturm, Ruger proudly introduced a 50th Anniversary Commemorative re-run of the original Flattop Blackhawk, updated only to current safety standards (including Sturm, Ruger's new keyed action lock).
(Around $600 MSRP, but there's a waiting list and you'll likely hafta pay up some if you wanna actually get one)
My own Blackhawk is over 40 years old (1962 production serial number, bought new in '64), and over those years, its brought down a pretty fair quantity of fairly large-sized game critters. Does a helluva job on things like old refrigerators, too. For hunting, I do use a very high performance .44 Magnum load, but for plinking and target practice, I'm kind to myself and use a much lighter .44 Special load. Helluva difference in recoil and muzzle flash ... nowhere near as loud, either, and quite a bit cheaper to boot.
As for older types, while range is nowhere up to modern standards, within a hundred yards or so the stopping power - foot-pounds of energy delivered to the target - of a black-powder .44 is on a par with just about anything of similar caliber available today, and though the penetration isn't all that great by current standards, that's a big part of why it hits so hard; it's a massive projectile which does not pass through the target, but rather imparts all its energy to the target. Not saying I'd take one on a bear hunt, mind you - just that in a pinch, it'd very likely work well enough.