The American Revolution (1775-1783) was the effort of some British colonists to start their independent government in America (and get rid of taxes). Many things caused the American Revolution, but these are some main ones.
Twelve years before the American Revolution, Britain and France fought a war that was called the French and Indian war (the Seven Years War). This might not seem like a big factor in the American Revolution, but it was. George Washington got his first military action in this war, and it was the reason the British were taxing the people, so they could repay the debts they amassed in the war.
Another cause for this revolution was the Royal Proclamation of 1763, a law that forbade settlers from moving on the other side of the Appalachian Mountains, into Indian territory. Most people ignored this law, however.
The Stamp Act was another law that annoyed the settlers greatly. For a document to be official, a stamp had to be purchased and placed on the document. This was basically a tax for the government to get back the money they lost defending their settlers from the French (which almost bankrupted Parliament).
The Townshend Act was yet another round of taxes the British imposed on their settlers to pay for the Seven Years War. This act not only implemented taxes on imported goods, but it also required settlers to house the British soldiers free of charge.
The Boston Massacre happened when an American patriot was harassing a British soldier who was standing guard. The soldier's friend (Hugh White) came over and tried to defend the guard, and eventually got so annoyed on the patriot that he hit him. At this, a mob formed and started hurling large blocks of ice at White. Soon, White was surrounded by angry Bostonians threatening to kill him. When White called for reinforcements, a British captain named Thomas Preston and some other soldiers entered the mob. They were cornered, and people with clubs joined the mob, threatening to attack the soldiers and challenging them to fire. One of the people threw a club and knocked down a British soldier, who got back up and fired into the mob. At this, the mob rushed the soldiers, and they had to fire to avoid getting beaten. Later, the soldiers were tried but acquitted because they fired as an act of self-defense. Parliament later repealed all taxes except the one on tea.
The Boston Tea Party happened when a crowd of patriots, dressed as Indians, mobbed tea ships and dumped the tea into the Boston Harbor to protest against the tea tax. Several ships carrying tea to the colonies returned to England to avoid being raided.
These are some causes of the American Revolution.