In the late 1960s, researchers at Stanford and UCLA connected two computers for the very first time. The computers were connected using ARPANET, or the Advanced Research Project Agency Network, an early packet-switching network funded by the U.S. Defense Department. After Stanford and UCLA successfully connected via ARPANET, other universities followed suit and joined the network. This was the early ancestor to the Internet.
A working computer with ARPANET connectivity, circa 1970. Image Source: Computer History Museum