Bob, Wilsons and Cudahy had multiple plants and branch houses around country. So their cars could be seen just about anywhere.
Rath had only one plant, the one in Waterloo, but it was the largest slaughter operation "under one roof" in the world, with
ability to load 124 cars in one day. So I suspect that Rath cars were see in multiple locations, also.
Remember the large packing houses worked very hard to develop and promote a brand name so housewives would ask for that brand at
their super market or butcher. They would market product across the country. In the 50's the population base (ie customers) was
still the north east, there were hungry folks everywhere. And while LA, San Francisco and Portland OR had slaughter operations,
most meat was still coming out of the mid-west, ie Chicago, Omaha, Kansas City, Sioux City, etc.
You might want to check the local newspaper (ask the library) for your time period to see what the grocery store ads list for name
brand meats, ie hams, bacon, etc. That will tell you what reefers came to town.
By the way I am now living much closer to Iowa City.