# ARPANET first message transmission history

> Developing situation record from CLSTR: https://clstr.news/situations/arpanet-first-message-transmission-history
> Updated: 2026-10-29T09:20:00.000Z. Sources: 41. Developments: 2.

On October 29, 1969, the first message was transmitted between two computers via ARPANET, the precursor to the modern internet. The transmission occurred at 10:30 PM local time, connecting a computer at the University of California, Los Angeles (UCLA) to one at the Stanford Research Institute in Menlo Park, California.

Programmer Charley Kline attempted to log in to the remote system by typing the command ‘LOGIN’. However, the system crashed after the first two letters were transmitted, meaning the very first message sent over the network was simply ‘LO’. 

Professor Leonard Kleinrock, who led the UCLA team, noted that while the crash prevented the full command from being sent, the connection was successfully re-established about an hour later. The accidental ‘LO’ message has since taken on symbolic meaning, echoing the English phrase ‘lo and behold’.

## Timeline

### 2026-10-29: ARPANET history: The first internet message sent in 1969

The first message sent over ARPANET in 1969 was the two-letter string ‘LO’, following a system crash during a login attempt between UCLA and Stanford.

2 sources. https://clstr.news/cluster/arpanet-history-the-first-internet-message-sent-in-1969

### 2026-10-29: Buenos Aires to host third Heritage Week in November

Buenos Aires will celebrate its third Heritage Week from November 2 to 8, 2026, offering free tours, workshops, and lectures to promote the city's architectural and cultural history.

39 sources. https://clstr.news/cluster/historical-anniversaries-of-black-tuesday-and-the-first-arpanet-message

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Cite as: ARPANET first message transmission history. CLSTR, https://clstr.news/situations/arpanet-first-message-transmission-history