“By the rude bridge that arched the flood,

Their flag to April’s breeze unfurled,

Here once the embattled farmers stood

And fired the shot heard round the world.”

That’s the opening of Ralph Waldo Emerson’s “Concord Hymn,” which commemorates the start of the Revolutionary War, which began 250 years ago Saturday.

You probably know the political reasons behind the American colonists' fight for independence. But there were major economic grievances as well.

In the mid-1700s America, if you were a white man with rights, the economy probably felt pretty good.

“Free colonists, who are living in the colonies in the 1760s, think they're part of the greatest empire since Rome because they have access to trade networks that are global,” said Scott Stephenson, president and CEO of the Museum of the American Revolution in Philadelphia.

He said back then, if you had enough money, you could get the same luxury goods in Philly you could in London.

But for all the perks, there were major problems for colonists trying to make their own way.

“It was illegal for colonial Americans to produce finished goods from many of the many of the raw materials,” said Stephenson.

That was especially galling, said Stephenson, for colonists in the mid-Atlantic region.

“We would have furnaces that would produce raw pig iron, but then that had to be shipped back to England to be produced into finished goods and then re-exported and brought back to the colonies,” said Stephenson.

Not to mention Great Britain and its parliament were coming off a major war that solidified its global empire and had it leaning on the colonies for funds.

“But what Parliament did to fund the standing army was to ratify a series of taxation policies, the first of which was the Sugar Act of 1764,” said Justene Hill Edwards, who teaches history at the University of Virginia.

The rules ended up taxing all sorts of sugar products, like rum and molasses, treats of 18th-century America.

“And then from there, we have the Stamp Act that was ratified in 1765, and this was an act essentially on paper products, newspapers, legal documents, bills of sale for goods and for slaves were being taxed, and at an additional rate,” said Hill Edwards.

Yes — some of the colonists demanding freedom were mad their sales receipts for buying slaves were being taxed at a higher rate.

Then the British messed with the caffeine supply:

“The Tea Act of 1773, and when colonists in Boston heard about this, they decided to to kind of reject it in a very public way, by throwing tea in into the Boston Harbor,” said Hill Edwards.

And that economic story of the American Revolution is probably pretty familiar.