"BITNET was a co-operative university computer network in the United States founded in 1981 by Ira Fuchs at the City University of New York (CUNY) and Greydon Freeman at Yale University."

https://en.wikipedia.org/wiki/BITNET

BITNET connected mainframes, had gateways to the Unix world and was still active in the 90s. And limited line lengths … some may remember SYSIN DD DATA … oh my goodness …

https://www.ibm.com/docs/en/zos/2.1.0?topic=execution-systsi...