There was one south of the town I grew up in. It was owned by the local butcher. It was very small and designed to process one cow at a time.
It was made out of concrete blocks painted white with one door at the end. The dimensions were approximately 16' x 8'.
Joe
PS. It was serviced by truck only, but there is no reason your's couldn't be rail served.
Swift had smaller "branch" meat plants across the country, they would bring in sides of beef in meat reefers and would cut them into steaks, roasts, etc - which would supply the local stores and restaraunts. The move to "boxed beef" in the 70s from packers like IBP led to the demise of these facilities.
RockIslandSorry, I don't have any more info on number of cattle pens they had and the rest of the process.
Rich
Alton Junction
I think the posts already submitted kinda point out the problem - a meat packing plant as small as you probably need would be too small to ship by rail. A small town back then would be more likely to have a stockpen / loading ramp for loading livestock into stock cars than to have a packing plant.
Keep in mind mechanical refrigerators capable of freezing meat or other food products were still a fairly new thing in the fifties, most reefer cars (wood or steel) were still cooled by ice, so couldn't keep things like sides of beef frozen. The animals had to be transported alive to huge stockyards (like Kansas City, Chicago, or South St. Paul) located near big slaughterhouse / meat packing plants.
In the 1970's I grew up in a small farm town in North Western Illinois. Some summers my Dad would take me to a slaughter house located in Lena, Illinois. It did not have train access only a truck chute. The overall building was probably around 50 ft X 50 ft. The large animal slaughter room was about 15 ft X 15 ft. They would slaughter one cow or pig at a time. The cows were brought into the slaughter chute, stunned, then they would fall onto the cart. Hind legs chained up to a pulley track system on the ceiling and pulled up. Then the throat was cut and while the cow was bleeding out, the skin would be removed and the carcuss cut in half. The Government inspector would do his job and stamp the cow halves and then the cow would get pushed into the refrigerator section of the building. This process would take about 15 to 20 minutes, then repeat with the next cow. Pigs were let loose in the room and shot with a 22 rifle and the rest of the process was the same for the pigs. Sorry, I don't have any more info on number of cattle pens they had and the rest of the process.
Ray Breyer
Modeling the NKP's Peoria Division, circa 1943