Here I thought gnomes had always been a PC race in D&D...hmmm, I guess I just figured they were a base race in 4E.
Not base in the 4E PH. The list for 4E PH is: dragonborn, dwarf, eladrin, elf, half-elf, halfling, human, and tiefling. PH2 adds deva, gnome, goliath, half-orc, and shifter.
The Monster Manual also gives stats for pcs of the following races: bugbear, doppleganger, drow, githyanki, githzerai, gnoll, gnome, goblin, hobgoblin, kobold, minotaur, orc, shadar-kai, shifter-longtooth, shifter-razorclaw, and warforged. MM2 adds bullywug, duergar, and kenku.