Ya know I never really knew if the story I tell about that concert is true, I do distinctly remember the emcee announcing it was Led Zep's first gig in the US (but then again I was just a bit tripped out). Welp a little research on Wiki tonight and voila:
Early years (1968–70)
On 14 October 1968, the band announced the new name and played their first show at the University of Surrey in Guildford on 25 October; this was followed by a short British tour.[28]Richard Cole organized their first North American tour at the end of the year, and would become a major figure in the touring life of the group.[29] The first show was in Denver on 26 December 1968, followed by other East Coast dates before they moved to California to play Los Angeles and San Francisco,http://en.wikipedia.org/wiki/Led_zeppelin#Early_years_.281968.E2.80.9370.29