Paul Schirmer's Used Cars in Warsaw was JO 7-5461; Hendrix McDanell Used Cars was JO 7 5051. Carl Varble's in Sparta was NI 3-2181. Glencoe Post Office was, and is, NI 3-4941.
That's why there are letters are phone dials.
The words “Jordan,” ie. 56, and “Niagara, ” ie. 64, were the names of the exchange you were in. To go from your exchange to another exchange, you dialed the first two letters of the exchange, plus the five digit number. Inside the exchange, you could just dial the five digit number. It explains why today, phones in a given area generally all start with the same two numbers – it’s the vestige of the old exchange names.