Hartz was born in Youngstown, Ohio, the son of Russian Jewish immigrants, but grew up in Omaha, Nebraska. After graduating from Technical High School in Omaha, he attended Harvard University, financed partly by a scholarship from the Omaha World Herald.
Hartz graduated in 1940, spent a year traveling abroad on a fellowship, then returned to Harvard as a teaching fellow in 1942. He earned his doctorate in 1946 and became a full professor of government in 1956. Hartz was known at Harvard for his talented and charismatic teaching. He retired in 1974 due to ill health and spent his last years living in London, New Delhi, New York, then Istanbul, where he died.
Hartz is best known for his classic book The Liberal Tradition in America (1955) which presented a view of America's past that sought to explain its conspicuous absence of ideologies. Hartz argued that American political development occurs within the context of an enduring, underlying Lockean liberal consensus, which has shaped and narrowed the landscape of possibilities for U.S. political thought and behavior. He attributed the triumph of the liberal worldview in America to its lack of a feudal past, and thus the absence of a struggle to overcome a conservative internal order; to its vast resources and open space; and to the liberal values of the original settlers, who represented only a narrow middle-class slice of European society.
Hartz was chiefly concerned with explaining the failure of socialism to become established in America, and believed that Americans' pervasive, unthinking consensual acceptance of classic liberalism was the major barrier. Hartz rejected Marxism, indeed turned it upside down, finding in the power of an idea the explanation of that inexplicable nonevent for Marxists, the absence of socialism in America.
In The Founding of New Societies (1964), Hartz developed the idea that the nations that developed from settler colonies were European "fragments" that in a sense froze the class structure and underlying ideology prevalent in the mother country at the time of their foundation, not experiencing the further evolution experienced in Europe. He considered Latin America and French Canada to be fragments of feudal Europe, the United States, English Canada, and Dutch South Africa to be liberal fragments, and Australia and English South Africa to be "radical" fragments (incorporating the non-Socialist working class radicalism of early 19th century Britain).
In 1956 the American Political Science Association awarded Hartz its Woodrow Wilson Prize for The Liberal Tradition in America, and in 1977 gave him its Lippincott Prize, designed to honor scholarly works of enduring importance. The book remains a key text in the political science graduate curriculum in American politics in universities today, in part because of the extensive, long-running criticism and commentary Hartz's ideas have generated.
- Economic Policy and Democratic Thought: Pennsylvania 1776-1860. 1948. Harvard University Press.
- The Liberal Tradition in America: An Interpretation of American Political Thought since the Revolution. 1955. Harcourt, Brace. ISBN 978-0-15-651269-5
- The Founding of New Societies: Studies in the History of the United States, Latin America, South Africa, Canada, and Australia. 1964. Harcourt, Brace & World. (edited). OCLC 254767
- A Synthesis of World History, (Zurich, 1984).
- The Necessity of Choice: Nineteenth-Century Political Thought. Edited with an introduction by Paul Roazen. 1990. Transaction Publishers. ISBN 978-0-88738-326-7
Journal Articles 
- “Otis and Anti-Slavery Doctrine.” 1939. The New England Quarterly 12(4): 745-747.
- “Seth Luther: The Story of a Working-Class Rebel.” 1940. New England Quarterly 13(3): 401-418.
- “Goals for Political Science: A Discussion.” 1951. American Political Science Review 45(4): 1001-1005.
- “American Political Thought and the American Revolution.” 1952. American Political Science Review 46(2): 321-342.
- “The Reactionary Enlightenment: Southern Political Thought before the Civil War.” 1952. Western Political Quarterly 5(1): 31-50.
- “The Whig Tradition in America and Europe.” 1952. American Political Science Review 46(4): 989-1002.
- “The Coming of Age of America.” 1957. American Political Science Review 51(2): 474-483.
- “Conflicts within the Idea of the Liberal Tradition.” 1963. Comparative Studies in Society and History 5(3): 279-284.
- “American Historiography and Comparative Analysis: Further Reflections.” 1963. Comparative Studies in Society and History 5(4): 365-377.
- “The Nature of Revolution.” 2005 . Society 42(4): 54-61.
Studies of Hartz 
- Abbott, Philip. "Still Louis Hartz after All These Years: A Defense of the Liberal Society Thesis," Perspectives on Politics, Vol. 3, No. 1 (Mar., 2005), pp. 93–109 in JSTOR
- Ericson, David and Louisa Green, eds. The Liberal Tradition in American Politics: Reassessing the Legacy of American Liberalism. 1999. Routledge.
- Hulliung, Mark, ed. The American Liberal Tradition Reconsidered: The Contested Legacy of Louis Hartz (University Press of Kansas; 2010) 285 pages; essays by scholars that reevaluate Hartz's argument that the United States is inherently liberal.
- Kloppenberg, James T. "In Retrospect: Louis Hartz's "The Liberal Tradition in America," Reviews in American History, Vol. 29, No. 3 (Sept. 2001), pp. 460–478 in JSTOR
- Smith, Rogers. “Beyond Tocqueville, Myrdal and Hartz: The Multiple Traditions in America.” American Political Science Review 1993. 87(3): 549-566.
- Barber, Benjamin. 1986. “Louis Hartz.” Political Theory 14(3): 355-358.
- Margolick, David (January 24, 1986). "Louis Hartz of Harvard Dies: Ex-Professor of Government". The New York Times. p. 17. Retrieved April 2, 2011.
- Mark C. Carnes, ed. American National Biography: Supplement 2 (2005) p. 236
- Patrick, R., "II. Louis Hartz: The Final Years, the Unknown Work" in Political Theory , vol. 16 (3), (Aug 1988), p. 377.