The first major military engagement of the american revolution took place where

ANSWER:

The "first major military engagement of American Revolution" had taken place near Boston in Middlesex County in the province of Massachusetts Bay.

EXPLANATION:

The battles of "Lexington" and "Concord" were the 1st military engagements of the American Revolution. The battles occurred in the cities of Cambridge, Lexington, Concord, Menotomy and Lincoln. These battles marked the initiation of an armed conflict between "Great Britain and 13 American colonies". The 13 colonies defeated the British and gained independence from "Great Britain".  

Primary sources are usually  more accurate and are written by someone who experienced it or witnessed it. secondary sources are those who heard of it after the fact that can lose details and or twist the event in a light that benefits them.