The Network That Started It All
ARPANET, the Advanced Research Projects Agency Network, was the first operational packet-switched computer network and the direct precursor to the modern internet. Funded by the United States Department of Defense's Advanced Research Projects Agency and first connected in October 1969, ARPANET linked research computers at four universities — UCLA, Stanford Research Institute, UC Santa Barbara, and the University of Utah — enabling researchers at these institutions to share computing resources and communicate electronically for the first time. The project was driven not primarily by military concerns, as popular mythology sometimes suggests, but by the scientific community's desire to share expensive computing resources and collaborate more effectively across geographic distances.
The key technical innovation underlying ARPANET was packet switching, a method of transmitting data by breaking messages into small packets that travel independently through the network and are reassembled at their destination. This approach, developed independently by Paul Baran at RAND Corporation and Donald Davies at the UK's National Physical Laboratory, was fundamentally different from the circuit-switched telephone networks of the era, which established dedicated connections between communicating parties. Packet switching used network capacity far more efficiently, could route around damaged or congested links, and allowed multiple communications to share the same physical infrastructure simultaneously. These properties made the network robust, scalable, and adaptable — qualities that would prove essential as the network grew from four nodes to billions of connected devices.
ARPANET's legacy extends far beyond its role as a communication network. The project fostered the development of foundational internet protocols including TCP/IP, designed by Vint Cerf and Bob Kahn, which provided a universal language for computer communication that remains the basis of the internet today. Email, invented by Ray Tomlinson in 1971 as a way to send messages between ARPANET users, became the network's most popular application and the first killer app of networked computing. The collaborative culture of the ARPANET research community, which valued open standards, shared development, and peer review, established norms that would shape internet governance and open-source software development for decades. By the time ARPANET was formally decommissioned in 1990, its protocols and principles had already been adopted by thousands of networks worldwide, forming the foundation of the global internet.