The Constitutional Convention was held during the summer of 1787. It was clear towards the end of 1786 that The Articles of Confederation was in need of severe revision. During that summer in Philadelphia the delegates drafted a new document, The United States Constitution. Some of the flaws in The Articles were its unicameral legislature, there was no executive or judicial branches. Under The Articles the federal government had no power to tax, or regulate trade. This flaw left the federal government at the mercy of the states. There were several different currencies being used, none of which had a uniformity of value. The emphasis of The Articles of Confederation was on separate rather than union. In essence the articles created the federal government but gave it no real power, it was as if there were 13 separate United States' in The United States. This should give you a start, enotes provides much more of the information you will need to write your essay.
The US Constitution is an incredibly important document that is the foundation of our American government. In writing your essay, I would suggest beginning with a strong introduction discussing why the Constitution is so important, and then delve into the history of its beginnings in the body of your essay. It was written in 1787 by 55 men including James Madison, George Washington, and Alexander Hamilton, and sets up the government into 3 branches. It also (along with the Bill of Rights) sets up rights and freedoms for the people of this nation. Enotes has some excellent information and references on the Constitution, as listed below.
As a "motivator" (a line or two to interest your reader) for your essay, why not begin with a quote from Patrick Henry or Thomas Paine or Thomas Jefferson, quotes that allude to the lack of freedom of speech, or another part of what would become the U.S. Constitution. This reference will underscore the importance of the Constitution as well as introduce the need for such a document.
Here is one example from Patrick Henry's speech to the Virginia Convention on March 23, 1775:
It is only in this way [of freedom] that we can hope to arrive at truth, and fulfill the great responsibility which we hold to God and our country
You may wish to read Henry's entire speech as well as Paine's pamphlet, "Crisis, No. 1" which contains his famous line, "These are the times that try men's souls." In this work Paine exhorts the citizens to see that hoping that the British will be kind is an empty hope: "The blood of his children will curse his cowardice who shrinks back at a time when a little might have saved the whole..." Paine urges action; the British virtually have them as prisoners in their own homes, he claims. Freedom must be obtained.
Or, read Thomas Jefferson's "A Declaration by the Representatives of the United States of America, in General Congress Assembled" in which Jefferson states,
When, in the course of human events, it becomes necessary for one people to dissolve the political bands which have connected them with another, and to assume among the powers of the earth the separate and equal station to which the laws of nature and of nature's God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation....
Book Source: Holt, Rinehart, and Winston Elements of Literature. Vol.1 (2000); 101,108,116.
The Constitution was borne out of the failure of the "Articles of Confederation and Perpetual Union," first proposed by John Dickinson of Pennsylvania. Fearing that any central government would in time grow oppressive, the Articles described a government by a confederation of states, each of which would be free to abide or ignore the central government, as was the case nearly 100 years later with the establishment of the Confederate States of America during the Civil War. The Articles could not effectively resolve several issues facing these new United States; as a result, a Constitutional Convention met in 1787 to create a new central, federal government with limited powers over the states. Although many delegates had their hand in creating the new United States government, James Madison, otherwise known as "the Father of the Constitution," established the basic structure of 3 governmental branches with checks and balances, which were designed to curtail federal power, and maintain the powers of the states and the individuals within states. Individuals became "dual citizens," citizens of the state in which they lived and citizens of the United States.