Alexander Jameson of Indianapolis invented, in 1883, a beer bung with an expandable bag. patent. Ths "rubber bag" would prevent outside are from contacting the beer. We haven't a clue how this could be made well with the materials then available. Bottled CO2 just wasn't available back then.
"The combination, with a bung, a tube passing through said bung, and an air-tight bag attached to said tube, of a cylindrical metallic case formed of two or more separable sections hinged to said bung, and adapted to inclose said bag and to be separated by the expansion thereof, substantially as and for the purpose set forth".
Did you know a guy in Terre Haute invented the jockey box? Well, it's a bit larger than an ice-filled cooler but it also cools the barrel. Henry Hahn patented it in 1894.
"D is the beer worm inside the ice box. The lower end of the worm D is provided with a branch d projecting through the side of the ice box, and E is the beer faucet provided with a shank e which passes through the side of the case A and is coupled to the branch d by the union e'."
"If desired, the case A can be made of large size and adapted to hold several barrels of 70 beer, each provided with its own faucet and cooling worm."
"When the air pump is worked, air is So drawn through the ice in the ice box, and is forced through the air worm inside the ice box, and thence into the top part of the beer barrel. The air becomes very cold in its passage through the ice and through the air 85 worm, and cools the beer in the barrel by direct contact with it."
Back in 1906 Gary Braybrook of Ft. Wayne invented a better beer tap. He was a principal in the Auto Omnibus Company. Nothing like a tap with a Motometer on it. From the patent application:
"It is well known that both draft and bottle beer is exceedingly sensitive to extremes of temperature, and. when it is too warm it is unpalatable and unhealthful, and that when it is "chilled" it loses its brightness, brilliancy and effervescence, and injures its flavor, which is best maintained by a temperature of from 42° to 45° Fahrenheit.
"The principal novel feature of my invention resides in the construction and cooperative arrangement of a mercury thermometer with the controlling valve or a draft beer faucet, whereby both the dealer and the purchaser can readily at all times ascertain at a glance the exact temperature of the beverage."