It is hard to believe, but this is how hostname to IP address mappings where done in 1974: the DNS didnt’t exist at that time because it was invented 10 years later. (The following image comprises about a third of a page of the single-page scan; there’s a bit more here.) Note how each host even includes decent contact information, in case you had to contact the operators of a particular host. The format is documented in RFC 608.

DNS and hosts.txt :: 01 Apr 2011 :: e-mail