From another version of this question:
/u/uncovered-history and /u/Takeoffdpantsnjaket and /u/lord_mayor_of_reddit have previously answered
This is a popular question, and more answers would be welcome.
A common misconception about the Revolutionary War is that it was planned: that, from the outset, all those Founding Fathers had the goal of independence firmly in their minds. Instead, from the early voices of resistance and outbreaks of violence in Boston there was an escalation of revolt and British reprisal that grew and finally made the War impossible to stop. The Continental Congress had been assembled to deal with the growing problem: in 1774 it had already sent a Petition to the King, begging for repeal of the Intolerable Acts, and that had been ignored ( possibly even unread, from Ben Franklin's account). But even after it had authorized an invasion of Canada, in July 1775 there were a number of members of the Congress who very much hoped to be able to strike a deal, the most important of which was John Dickinson of Pennsylvania. Dickinson was able to get one more petition drafted and sent, the Olive Branch Petition. But by the time it got to London the British government , with the active support of the King, had set itself on crushing the revolt, not negotiating.
This is why you can pick all sorts of dates as important for the movement towards independence. As well as the surrender at Yorktown another pretty good rival to July 4, 1776 would be November 15, 1777: that's when the Articles of Confederation were approved by the Congress, that created a national government.
If it's of interest to you, I've written about the battles of Lexington and Concord here before, and how the British administration in Boston came to a breaking point with the colonists. That provides some background to /u/Bodark43's post elsewhere in the thread about the slow boil that led to the independence movement.