The first 10 Amendments to the Constitution were known as the Bill of Rights.  They were essential to the passage of the Constitution because the Constitution would not have been ratified without the promise of a Bill of Rights. 
 

 The Bill of Rights, amendments, were arranged by James Madison, then a member of the House of Representatives, not in order of importance or preference, but according to the order of the provisions of the Constitution they were intended to modify; for Madison’s original plan, soon to be rejected by the House, was to incorporate the amendments into the constitutional text. 
 

The first ten amendments were added to the Constitution on December 15, 1791 to fulfill a promise. Massachusetts, New Hampshire, New York, and Virginia had only agreed to ratify the Constitution with the understanding that it would be amended to explicitly protect our most basic rights.

The Bill of Rights drew its influences from many of the liberties protected by state constitutions. the Virginia Declaration of Rights, the English Bill of Rights, the writings of the Enlightenment, and the rights defined in the Magna Carta. 

Not all of the earliest constitutions contained bills of rights, but the examples set by such States as Virginia, Pennsylvania, and Massachusetts set the trend for future constitutions.

The Virginia Declaration of Rights, drafted by George Mason, was the most widely hailed and served as the favored model for the rest of the nation. The provisions of this Declaration (and the other bills of rights) may be traced to Magna Charta, the Petition of Right, and the English Bill of Rights. It set forth the usual requirements regarding trial by jury, cruel and unusual punishments, search warrants, freedom of the press, and the subordination of the military to civil government. Separation of Powers was also listed as a right of the people, and it was further stipulated that all men who could demonstrate that they had a permanent common interest with the community—that is, were property owners—should be given access to the ballot. Another important provision guaranteed freedom of religion. This was added at the insistence of Patrick Henry and James Madison. Like the Declaration of Independence that Jefferson wrote shortly thereafter, the Virginia Declaration of Rights asserted that all authority is derived from the people, who have the inalienable right to reform the government if it fails to provide for their safety and happiness.
 

The Northwest Ordinance
The Ordinance has been called our first national bill of rights, or “the Magna Charta of American Freedom.” The great American statesman Daniel Webster said he doubted “whether one single law of any lawgiver, ancient or modern, has produced effects of more distinct, marked and lasting character than the Ordinance of 1787.”

It protected many civil liberties that later appeared in the Bill of Rights

It banned slavery in the Northwest Territory. The wording of the Thirteenth Amendment (1865) providing for the abolition of slavery in the United States was taken directly from the Northwest Ordinance.

On the subject of religion, the ordinance provided that “No person, demeaning himself in a peaceable and orderly manner, shall ever be molested on account of his mode of worship or religious sentiments, in said Territory.”

Sources: Reason.org: Happy Bill of Rights Day!, Yale Law: The American Constitution - A Documentary Record

"One of the principal points of contention between the Federalists and Anti-Federalists was the lack of an enumeration of basic civil rights in the Constitution."
-- Whitehouse.gov

Brutus made the following argument in antiFederalist No. 84 – On the Lack of a Bill of Rights

Those who have governed, have been found in all ages ever active to enlarge their powers and abridge the public liberty. This has induced the people in all countries, where any sense of freedom remained, to fix barriers against the encroachments of their rulers. The country from which we have derived our origin, is an eminent example of this. Their magna charta and bill of rights have long been the boast, as well as the security of that nation. I need say no more, I presume, to an American, than that this principle is a fundamental one, in all the Constitutions of our own States; there is not one of them but what is either founded on a declaration or bill of rights, or has certain express reservation of rights interwoven in the body of them. From this it appears, that at a time when the pulse of liberty beat high, and when an appeal was made to the people to form Constitutions for the government of themselves, it was their universal sense, that such declarations should make a part of their frames of government. It is, therefore, the more astonishing, that this grand security to the rights of the people is not to be found in this Constitution.

The defenders of the Constitution argued that a bill of rights would undermine the idea of a government with limited powers.

 
1)  A written constitution is the product of a social compact, which affirms that all authority originally resides in the people and that the people create a government of limited and enumerated powers in a written constitution.

2) Due to the impossibility of defining all of the rights which government must respect, a bill of rights would leave a window open for government to infringe upon the rights of its citizens.

3) There was no need for a declaration of rights in 1787, because the work had already been done in 1776 when in the Declaration of Independence, our Founders had declared that all human beings are endowed with natural and inalienable rights by virtue of their participation in the same fundamental human nature.

In Federalist 84, Alexander Hamilton made the following argument:

[A] Bills of rights, in the sense and in the extent in which they are contended for, are not only unnecessary in the proposed constitution, but would even be dangerous. They would contain various exceptions to powers which are not granted; and on this very account, would afford a colorable pretext to claim more than were granted. For why declare that things shall not be done which there is no power to do? Why for instance, should it be said, that the liberty of the press shall not be restrained, when no power is given by which restrictions may be imposed? I will not contend that such a provision would confer a regulating power; but it is evident that it would furnish, to men disposed to usurp, a plausible pretense for claiming that power.

Sources: Heritage.org: Securing Liberty - The Purpose & Importance of the Bill of Rights, Antifederalist No. 84 On The Lack of a Bill of Rights

For a more in depth analysis: Amendments to the Constitution: First Through Tenth Amendments

The Bill of Rights was a concession to the Anti-Federalists and to the States’ Rightists who feared Federal usurpation of State power, particularly in the sensitive area of civil liberties. By its terms, the Bill of Rights applied only to Congress (the Federal government) and exempted the States.

Viewed in historical perspective, its purpose was two-fold: (1) to assure each individual that the Federal government would not encroach upon his civil liberties, and (2) to assure each State that the Federal government would not have jurisdiction over most civil liberties disputes between a State and its citizens. Each amendment was a guarantee to the individual and to the States, limiting the powers of the Federal government but not those of the States. 

Resources: Answers.com: General Welfare Clause, Answers.com: Commerce Clause

It is important to understand precisely, so far as possible, the meanings intended by the men (chiefly James Madison and George Mason) whose phrases are found in the Bill of Rights, because many important cases of constitutional law that affect millions of Americans are today decided on the presumed significance of certain phrases in the Bill of Rights.
 

What did those words mean, as people used them near the end of the eighteenth century?

One way to find out is to consult the first great dictionary of the English language, Samuel Johnson’s, published at London in 1775; or, later, Noah Webster’s American Dictionary of the English Language (1828).
 

Another way to ascertain what the framers of the Bill of Rights intended by their amendments, and what the first Congress and the ratifying State legislatures understood by the amendments’ language, is to consult the following sources: 

▪ Sir William Blackstone’s Commentaries on the Laws of England (1765)

▪ The early Commentaries on the Constitution (1833) Joseph Story

▪ Commentaries on American Law (1826) James Kent.

What argument might a Federalist or Anti-Federalist make to defend individual or states’ rights against their encroachment due to Congress’ interpretation of the General Welfare or Commerce Clause in the Constitution?

Article I, section 8 of the U. S. Constitution grants Congress the power to lay and collect Taxes, Duties, Imposts, and Excises, to pay the Debts and provide for the common defense and general Welfare of the United States."

Since the late eighteenth century this language has prompted debate over the extent to which it grants powers to Congress that exceed those powers specifically enumerated in the Constitution.

This clause also authorizes Congress:

"To regulate Commerce with foreign Nations, and among the several States, and with Indian Tribes."

It is the legal foundation of much of the U.S. government's regulatory authority.