This might be stretching your definition a bit, but the earliest may be X.25 networks/PDNs (Telenet, Tymnet, etc.) or, even earlier, AlohaNET. https://en.m.wik

This might be stretching your definition a bit, but the earliest may be X.25 networks/PDNs (Telenet, Tymnet, etc.) or, even earlier, AlohaNET. https://en.m.wikipedia.org/wiki/Public_data_network https://en.m.wikipedia.org/wiki/Public_data_network https://en.m.wikipedia.org/wiki/ALOHAnet https://en.m.wikipedia.org/wiki/ALOHAnet