Origins of the Internet: From ARPANET to the World Wide Web
The Cold War Problem
In the late 1960s, the U.S. Department of Defense had a problem: its computing resources were scattered across universities and research labs, and there was no way for researchers to share them. The Advanced Research Projects Agency launched ARPANET in 1969 to connect these machines. The first message, sent from UCLA to Stanford Research Institute on October 29, was supposed to be "LOGIN" — but the system crashed after "LO."
ARPANET introduced two ideas that define the internet to this day. The first was packet switching: instead of establishing a dedicated circuit for each conversation like a phone call, data was broken into packets that could take different routes through the network and be reassembled at the destination. This made the network resilient to failure — if one node went down, packets could route around it. Paul Baran at RAND and Donald Davies in the UK developed packet switching independently around the same time.
TCP/IP and the Network of Networks
By the 1970s, multiple packet-switched networks existed — ARPANET, satellite networks, radio networks — but they couldn't talk to each other. Vint Cerf and Bob Kahn published the specification for TCP in 1974, later splitting it into TCP and IP. IP handled addressing and routing between networks; TCP handled reliable delivery within a connection. This "network of networks" architecture meant any network could join the internet by implementing TCP/IP, regardless of its underlying hardware.
On January 1, 1983, ARPANET switched to TCP/IP permanently. That date is often marked as the internet's true birthday. Throughout the 1980s, the National Science Foundation built NSFNET, a high-speed backbone connecting supercomputing centers, and the network grew from a few hundred nodes to tens of thousands.
The Web Layer
The internet is the infrastructure; the World Wide Web is an application that runs on top of it. In 1989, Tim Berners-Lee, a researcher at CERN, proposed a system for linking documents across the network using hypertext. He wrote the first web browser and web server, and specified three core technologies: HTML for formatting documents, URLs for addressing them, and HTTP for transferring them.
CERN released the web software into the public domain in 1993. That same year, Marc Andreessen and Eric Bina at NCSA released Mosaic, the first graphical browser that displayed images inline with text. Mosaic made the web accessible to non-technical users, and the growth curve went vertical. By 1995, the web carried more traffic than any other internet application.
The Edge Review explains history for general readers. Internet history is richly documented; sources include the Computer History Museum and original RFC specifications.