The network that was the precursor to the internet was ARPANET, short for Advanced Research Projects Agency Network. Created by the U.S. Advanced Research Projects Agency, it was an early wide-area packet-switched network and a direct foundation for today’s internet.
The ARPANET project began in the late 1960s to let researchers share computing resources across distant institutions. Its first four connected nodes were established in 1969 at UCLA, the Stanford Research Institute, UC Santa Barbara, and the University of Utah. The first message was sent between UCLA and SRI in October 1969, although the attempted word “login” famously failed after the letters “lo.”
ARPANET initially used the Network Control Program. On January 1, 1983, it adopted TCP/IP, a major milestone because the protocol suite allowed separate networks to interconnect as a larger “network of networks.”
ARPANET was not identical to the modern internet, and other networks such as NSFNET also played important roles. It was formally decommissioned in 1990, by which time commercial and academic networks were carrying the internet forward.