I'll admit when I'm wrong - I knew those dates, but it didn't parse that they were post-1775. In any case, the USMC was in operation prior to 1775, though not under the USMC (at the time, Continental Marines) banner; the official recognition and formation into a coherant and centrally directed fighting force took place after many had already been fighting under different banners but performing similar missions.
You can always tell a lefty....
But you can't tell them much...