After the Civil War, weapons factory owners realized that no war meant no profits. So they came up with the idea to replace bullets with sound-making caps and sell the guns as a novelty item.
Those guns were loud, but they didn't shoot anything. That was fixed by harnessing pneumatic technology to make air rifles that blasted ball bearings of 0.18 inches (a size halfway between B and BBB shotgun shot -> BB gun). In 1888, the floundering Plymouth Iron Windmill Co. in Michigan decided to include a BB gun as a freebie with every farmer's order, and in two years, Plymouth had shut down windmill production and was manufacturing 50,000 Daisy Air Rifles a year, "daisy" being the "awesome" of 1888.
The noteworthy thing about turn-of-the-century Daisy-type guns, said Penn State history professor Gary Cross, is that these "toys" were marketed to adults. One 1890 catalog billed its air rifle as "just the thing to make the neighbor's cat scratch and growl and doggy fly for home"; another similar rifle was advertised as a parlor game. Pest control and family entertainment, not shoot-'em-ups in the back yard.
One of the most famous BB guns is the Red Ryder BB Gun by Daisy Outdoor Products, modeled after the western Winchester rifle. First introduced in 1938, the BB gun became an iconic American toy, and is still in production today.
What's it worth? Take a look at this Daisy Air Rifle price guide: sold listings for a value indication.