Communication · 1969
ARPANET
UCLA sends 'LO' to Stanford before crashing: the first message of the internet's ancestor.
On 29 October 1969 the first ARPANET link connected UCLA and SRI, using packet-switching Interface Message Processors built by BBN. Funded by the US Defense Department's ARPA, it grew to dozens of sites and became the testbed for email, TCP/IP and internet culture.
What it built on 3
What it led to 2
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Related measurements
The dashed line marks when it first worked.
Internet users in the United States Latest: 322M people (2024) Source: Our World in Data
Share of people online Latest: 73.6 % (2025) Source: Our World in Data