Perhaps his greatest contribution was the separation of church and state. In his time, heresy was a capital offense in Virginia. No Jews, Catholics, or Quakers could hold office in New England. Jefferson advanced the radical notion, and codified it in law, first in Virginia, then nationally, that religion should be a matter of personal conscience between the individual and his conception of God, not a matter for the state to decide.

Perhaps his greatest hypocrisy was his ownership of slaves and his failure throughout his life or even at the end of it to free a single slave. When he wrote the Declaration of Independence in 1776, 539,000 Americans, roughly 1 in 5, were slaves.

Jefferson had a romanticized view of the agrarian state. He failed to foresee or understand the role of industrialization and manufacturing, but he could hardly be blamed for this, since the Industrial Revolution was born only during the final years of his life and affected the country along sharply regional lines. In his view, gentlemen farmers (white males supported by legions of slaves) would rule their estates, generally left alone by a small central government, free to tinker, to explore, to read. He was somewhat of a dilettante, interested in many things, but ultimately a failure at the business of making his farm profitable. He died so deeply in debt not only could he not free his slaves, but he had to sell many of them, breaking up families, to pay off his debts.

His arch rival, who favored a strong central government and - despite his illegitimate birth - aristocracy and its principles, was Alexander Hamilton, perhaps the greatest Secretary of the Treasury ever. Hamilton of course was was killed by Aaron Burr in a duel in 1804.

Jefferson doubled the size of the United States by negotiating the Louisiana Purchase in 1803.

He was a member of the Virginia House of Burgess, served as the Governor of Virginia from 1779-81, Congressman, Minister to France (1785), and Secretary of State from 1789-1793.

He served as a delegate to the 2nd Continental Congress in 1775, and was chosen to write the Declaration of Independence.

Jefferson served as the 3^rd President of the United States from 1801-1809, but didn't view this accomplishment as significant enough to put on his tombstone.

Jefferson formed the country's first political party, and ran as a Republican with a platform of egalitarian agrarianism and rationality against the Federalists. He ran against John Adams in 1796, and again in 1800, and was chosen for President by Congress after tying with Aaron Burr.

 Thomas Jefferson on Separation of Church and State

"The American Revolution was in many respects a manifestation of the Enlightenment in political, civil, and ecclesiastical action. One of its triumphs was the passage of the Virginia Statute for Religious Liberty in 1786 (which Jefferson, the original author, proudly had printed in the next edition of the French Encyclopédie). The state would tolerate all religions but give formal favour to none; people were free to follow the dictates of their own religious consciences. Although several states retained formal establishments, there was much competition among sects. In New England and in commercial centres of activity, and later in newer western settlements, the earlier severe Calvinism gradually gave way to a gentler and more indulgent universalism: people came to hope and then to believe that God actually wanted his creatures to be happy. Doctrinally, moreover, Unitarianism appealed to an increasing number of Congregationalists. A great new revivalist movement arose again around 1798, mainly in the new West, and this frequently renewed revival spirit appealed directly to the senses and away from the moderate intellectualism of the Enlightenment…

"He returned to Virginia in October 1776 and immediately launched an extensive project for the reform of the state's legal code to bring it in line with the principles of the American Revolution. Three areas of reform suggest the arc of his political vision: first, he sought and secured abolition of primogeniture, entail, and all those remnants of feudalismthat discouraged a broad distribution of property; second, he proposed a comprehensive plan of educational reform designed to assure access at the lowest level for all citizens and state support at the higher levels for the most talented; third, he advocated a law prohibiting any religious establishment and requiring complete separation of church and state. The last two proposals were bitterly contested, especially the statute for religious freedom, which was not enacted until 1786."

The Danbury Baptist Association, concerned about religious liberty in the new nation wrote to President Thomas Jefferson, Oct. 7, 1801.

Sir, Among the many millions in America and Europe who rejoice in your Election to office; we embrace the first opportunity which we have enjoyed in our collective capacity, since your Inauguration, to express our great satisfaction, in your appointment to the chief Majestracy in the United States; And though our mode of expression may be less courtly and pompious than what many others clothe their addresses with, we beg you, Sir to believe, that none are more sincere.
Our Sentiments are uniformly on the side of Religious Liberty -- That religion is at all times and places a matter between God and individuals -- That no man ought to suffer in name, person, or effects on account of his religious Opinions - That the legitimate Power of civil government extends no further than to punish the man who works ill to his neighbor: But Sir our constitution of government is not specific. Our ancient charter together with the Laws made coincident therewith, were adopted on the Basis of our government, at the time of our revolution; and such had been our Laws & usages, and such still are; that Religion is considered as the first object of Legislation; and therefore what religious privileges we enjoy (as a minor part of the State) we enjoy as favors granted, and not as inalienable rights: and these favors we receive at the expense of such degrading acknowledgements, as are inconsistent with the rights of freemen. It is not
to be wondered at therefore; if those, who seek after power & gain under the pretense of government & Religion should reproach their fellow men -- should
reproach their chief Magistrate, as an enemy of religion Law & good order because he will not, dare not assume the prerogatives of Jehovah and make
Laws to govern the Kingdom of Christ.
Sir, we are sensible that the President of the United States, is not the national legislator, and also sensible that the national government cannot destroy the Laws of each State; but our hopes are strong that the sentiments of our beloved President, which have had such genial affect already, like the radiant beams of the Sun, will shine and prevail through all these States and all the world till Hierarchy and Tyranny be destroyed from the Earth. Sir, when we reflect on your past services, and see a glow of philanthropy and good will shining forth in a course of more than thirty years we have reason to believe that America's God has raised you up to fill the chair of State out of that good will which he bears to the Millions which you preside over. May God strengthen you for the arduous task which providence & the voice of the people have called you to sustain and support you in your Administration against all the predetermined opposition of those
who wish to rise to wealth & importance on the poverty and subjection of the people.
And may the Lord preserve you safe from every evil and bring you at last to his Heavenly Kingdom through Jesus Christ our Glorious Mediator.
Signed in behalf of the Association.
Nehh Dodge
Ephram Robbins The Committee
Stephen S. Nelson

Baptists in Danbury, Connecticut were persecuted because they were not part of the Congregationalist establishment in that state.
On January 1, 1802, in response to the letter from the Danbury Baptist Association, Thomas Jefferson wrote:

Gentlemen:
The affectionate sentiments of esteem and approbation which are so good to express towards me, on behalf of the Danbury Baptist Association, give me
the highest satisfaction. My duties dictate a faithful and zealous pursuit of the interests of my constituents, and in proportion as they are persuaded of my fidelity to those duties, the discharge of them becomes more and more pleasing.
Believing with you that religion is a matter which lies solely between man and his God; that he owes account to none other for his faith or his worship; that the legislative powers of the government reach actions only, and not opinions, I contemplate with sovereign reverence that act of the whole American people which declared that their legislature should `make no law respecting an establishment of religion, or prohibiting the free exercise thereof," thus building a wall of separation between church and State. Adhering to this expression of the supreme will of the nation in behalf of the rights of conscience, I shall see with sincere satisfaction the progress of those sentiments which tend to restore man to all of his natural rights, convinced he has no natural right in opposition to his social duties.
I reciprocate your kind prayers for the protection and blessings of the common Father and Creator of man, and tender you and your religious association, assurances of my high respect and esteem.
Thomas Jefferson

Sources: Robert S. Alley, Professor of Humanities, Emeritus, University of
Richmond, from his article, "Public Education and the Public Good,"
published in William & Mary Bill of Rights Journal, Vol. 4, Issue 1, Summer
1995.
And Lipscomb, Andrew and Bergh, Albert, The Writings of Thomas Jefferson,
Vol. 16, pp. 281-282.