Missed this anniversary by only a few days. The Continental Army took Dorchester Heights on March 4th, 1776. It was such a commanding position that the British Army had to move. A storm prevented them from attacking (which is actually what Washington wanted), and they had to leave Boston.
I'm reading '1776' by David McCullough right now, and I found this part of the story absolutely thrilling: bringing all of that artillery hundreds of miles from Fort Ticonderoga, keeping the plan a secret, pre-building artifical 'embankments' and hauling them into place. Cool story!
If you're lucky, you'll get more reports like this as I read through the book ;-)
UPDATE: Can't believe y'all let me spell McCullough wrong! But don't worry, I fixed it. Hello? Is this thing on?