Oldest cache of assorted types as far as I know. Types were invented after the caches had existed for a while, and cache owners were able to change types, so determining first for each type is a confused exercise.
Originally, all caches were listed as Geocache.
May 7, 2001, Jeremy added cache types. See this forum thread, Cache Types
Created at that time:
Traditional, Multi-cache, Letterbox hybrid, Virtual, Unknown, Event
Also in May 01, A.P.E. caches, then Webcams (Jan or Feb 02), Locationless (4/02), CITO events (4/03), Earthcaches (1/04), MEGA event (5/06), GPS Maze (6/07), Wherigo (1/08), 10 Year Events (5/10), and special HQ cache and HQ event icons.
Good info in this Oct 04 forum thread
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