Question: What Columbia President went to the university that hired the person who declared the American frontier "closed" in 1893?

full_context: Document 1: Chalisa famine: Together the two famines may have depopulated many regions of India, including, for example, 17 per cent of the villages in the Sirkali region of present-day Tamil Nadu, 60 per cent of the villages in the middle Doab of present-day Uttar Pradesh, and over 30 per cent of the villages in the regions around Delhi. It is thought that up to 11 million people may have died in the two famines.
Document 2: Historical rankings of presidents of the United States: According to a Rasmussen poll conducted in 2007, six presidents -- George Washington, Abraham Lincoln, Thomas Jefferson, Theodore Roosevelt, Franklin D. Roosevelt, and John F. Kennedy -- were rated favorably by at least 80% of Americans.
Document 3: The Significance of the Frontier in American History: ``The Significance of the Frontier in American History ''is a seminal essay by the American historian Frederick Jackson Turner which advanced the Frontier Thesis of American history. It was presented to a special meeting of the American Historical Association at the World's Columbian Exposition in Chicago, Illinois in 1893, and published later that year first in Proceedings of the State Historical Society of Wisconsin, then in the Annual Report of the American Historical Association. It has been subsequently reprinted and anthologized many times, and was incorporated into Turner's 1921 book, The Frontier in American History, as Chapter I.
Document 4: Carl Kaestle: Carl Frederick Kaestle (born March 27, 1940) is University Professor and Professor of Education, History, and Public Policy emeritus at Brown University. His historical research has focused on the development of American schools, particularly in the 1800s. He has worked at the University of Chicago and University of Wisconsin–Madison and is a former president of the National Academy of Education.
Document 5: Harvard University: Other: Civil rights leader W. E. B. Du Bois; philosopher Henry David Thoreau; authors Ralph Waldo Emerson and William S. Burroughs; educators Werner Baer, Harlan Hanson; poets Wallace Stevens, T. S. Eliot and E. E. Cummings; conductor Leonard Bernstein; cellist Yo Yo Ma; pianist and composer Charlie Albright; composer John Alden Carpenter; comedian, television show host and writer Conan O'Brien; actors Tatyana Ali, Nestor Carbonell, Matt Damon, Fred Gwynne, Hill Harper, Rashida Jones, Tommy Lee Jones, Ashley Judd, Jack Lemmon, Natalie Portman, Mira Sorvino, Elisabeth Shue, and Scottie Thompson; film directors Darren Aronofsky, Terrence Malick, Mira Nair, and Whit Stillman; architect Philip Johnson; musicians Rivers Cuomo, Tom Morello, and Gram Parsons; musician, producer and composer Ryan Leslie; serial killer Ted Kaczynski; programmer and activist Richard Stallman; NFL quarterback Ryan Fitzpatrick; NFL center Matt Birk; NBA player Jeremy Lin; US Ski Team skier Ryan Max Riley; physician Sachin H. Jain; physicist J. Robert Oppenheimer; computer pioneer and inventor An Wang; Tibetologist George de Roerich; and Marshall Admiral Isoroku Yamamoto.
Document 6: Caribbean and Central America Action: Among the public figures speaking at the 33rd conference, held in 2009 in Miami, were the Prime Minister of Haiti, Jean-Max Bellerive, Canada's Minister of State of Foreign Affairs, Peter Kent and Puerto Rico's Secretary of State, Kenneth McClintock. The organization's policy-oriented programs have focused on tourism, financial services, policy and regulatory environments for business in the Americas, energy security, maritime port security, disaster mitigation, customs, telecommunications, intellectual property rights, information technology, agriculture and telecommunications. Cabinet-level officials have represented the United States at prior conferences.
Document 7: Oklahoma: During the 1930s, parts of the state began suffering the consequences of poor farming practices, extended drought and high winds. Known as the Dust Bowl, areas of Kansas, Texas, New Mexico and northwestern Oklahoma were hampered by long periods of little rainfall and abnormally high temperatures, sending thousands of farmers into poverty and forcing them to relocate to more fertile areas of the western United States. Over a twenty-year period ending in 1950, the state saw its only historical decline in population, dropping 6.9 percent as impoverished families migrated out of the state after the Dust Bowl.
Document 8: University of Chicago: Notable alumni in the field of government and politics include the founder of modern community organizing Saul Alinsky, Obama campaign advisor and top political advisor to President Bill Clinton David Axelrod, Attorney General and federal judge Robert Bork, Attorney General Ramsey Clark, Prohibition agent Eliot Ness, Supreme Court Justice John Paul Stevens, Prime Minister of Canada William Lyon Mackenzie King, 11th Prime Minister of Poland Marek Belka, Governor of the Bank of Japan Masaaki Shirakawa, the first female African-American Senator Carol Moseley Braun, United States Senator from Vermont and 2016 Democratic Presidential Candidate Bernie Sanders, and former World Bank President Paul Wolfowitz.
Document 9: Amazon rainforest: For a long time, it was thought that the Amazon rainforest was only ever sparsely populated, as it was impossible to sustain a large population through agriculture given the poor soil. Archeologist Betty Meggers was a prominent proponent of this idea, as described in her book Amazonia: Man and Culture in a Counterfeit Paradise. She claimed that a population density of 0.2 inhabitants per square kilometre (0.52/sq mi) is the maximum that can be sustained in the rainforest through hunting, with agriculture needed to host a larger population. However, recent anthropological findings have suggested that the region was actually densely populated. Some 5 million people may have lived in the Amazon region in AD 1500, divided between dense coastal settlements, such as that at Marajó, and inland dwellers. By 1900 the population had fallen to 1 million and by the early 1980s it was less than 200,000.
Document 10: Great Plains: The 100th meridian roughly corresponds with the line that divides the Great Plains into an area that receive 20 inches (510 millimetres) or more of rainfall per year and an area that receives less than 20 in (510 mm). In this context, the High Plains, as well as Southern Alberta, south-western Saskatchewan and Eastern Montana are mainly semi hot steppe land and are generally characterised by rangeland or marginal farmland. The region (especially the High Plains) is periodically subjected to extended periods of drought; high winds in the region may then generate devastating dust storms. The eastern Great Plains near the eastern boundary falls in the humid subtropical climate zone in the southern areas, and the northern and central areas fall in the humid continental climate.
Document 11: Education: In time, some ideas from these experiments and paradigm challenges may be adopted as the norm in education, just as Friedrich Fröbel's approach to early childhood education in 19th-century Germany has been incorporated into contemporary kindergarten classrooms. Other influential writers and thinkers have included the Swiss humanitarian Johann Heinrich Pestalozzi; the American transcendentalists Amos Bronson Alcott, Ralph Waldo Emerson, and Henry David Thoreau; the founders of progressive education, John Dewey and Francis Parker; and educational pioneers such as Maria Montessori and Rudolf Steiner, and more recently John Caldwell Holt, Paul Goodman, Frederick Mayer, George Dennison and Ivan Illich.
Document 12: Frederick Jackson Turner: Frederick Jackson Turner (November 14, 1861 – March 14, 1932) was an American historian in the early 20th century, based at the University of Wisconsin until 1910, and then at Harvard. He was primarily known for his “Frontier Thesis.” He trained many PhDs who came to occupy prominent places in the history profession. He promoted interdisciplinary and quantitative methods, often with a focus on the Midwest. He is best known for his essay "The Significance of the Frontier in American History", whose ideas formed the Frontier Thesis. He argued that the moving western frontier shaped American democracy and the American character from the colonial era until 1890. He is also known for his theories of geographical sectionalism. In recent years historians and academics have argued strenuously over Turner's work; all agree that the Frontier Thesis has had an enormous impact on historical scholarship and the American soul.
Document 13: Harvard University: Politics: U.N. Secretary General Ban Ki-moon; American political leaders John Hancock, John Adams, John Quincy Adams, Rutherford B. Hayes, Theodore Roosevelt, Franklin D. Roosevelt, John F. Kennedy, Al Gore, George W. Bush and Barack Obama; Chilean President Sebastián Piñera; Colombian President Juan Manuel Santos; Costa Rican President José María Figueres; Mexican Presidents Felipe Calderón, Carlos Salinas de Gortari and Miguel de la Madrid; Mongolian President Tsakhiagiin Elbegdorj; Peruvian President Alejandro Toledo; Taiwanese President Ma Ying-jeou; Canadian Governor General David Lloyd Johnston; Indian Member of Parliament Jayant Sinha; Albanian Prime Minister Fan S. Noli; Canadian Prime Ministers Mackenzie King and Pierre Trudeau; Greek Prime Minister Antonis Samaras; Israeli Prime Minister Benjamin Netanyahu; former Pakistani Prime Minister Benazir Bhutto; U. S. Secretary of Housing and Urban Development Shaun Donovan; Canadian political leader Michael Ignatieff; Pakistani Members of Provincial Assembly Murtaza Bhutto and Sanam Bhutto; Bangladesh Minister of Finance Abul Maal Abdul Muhith; President of Puntland Abdiweli Mohamed Ali; U.S. Ambassador to the European Union Anthony Luzzatto Gardner.
Document 14: Great Plains: The rural Plains have lost a third of their population since 1920. Several hundred thousand square miles (several hundred thousand square kilometers) of the Great Plains have fewer than 6 inhabitants per square mile (2.3 inhabitants per square kilometer)—the density standard Frederick Jackson Turner used to declare the American frontier "closed" in 1893. Many have fewer than 2 inhabitants per square mile (0.77 inhabitants per square kilometer). There are more than 6,000 ghost towns in the state of Kansas alone, according to Kansas historian Daniel Fitzgerald. This problem is often exacerbated by the consolidation of farms and the difficulty of attracting modern industry to the region. In addition, the smaller school-age population has forced the consolidation of school districts and the closure of high schools in some communities. The continuing population loss has led some to suggest that the current use of the drier parts of the Great Plains is not sustainable, and there has been a proposal - the "Buffalo Commons" - to return approximately 139,000 square miles (360,000 km2) of these drier parts to native prairie land.
Document 15: Frederick Winslow Taylor: Frederick Winslow Taylor (March 20, 1856 -- March 21, 1915) was an American mechanical engineer who sought to improve industrial efficiency. He was one of the first management consultants. Taylor was one of the intellectual leaders of the Efficiency Movement and his ideas, broadly conceived, were highly influential in the Progressive Era (1890s - 1920s). Taylor summed up his efficiency techniques in his 1911 book The Principles of Scientific Management, which in 2001 Fellows of the Academy of Management voted the most influential management book of the twentieth century. His pioneering work in applying engineering principles to the work done on the factory floor was instrumental in the creation and development of the branch of engineering that is now known as industrial engineering. Taylor made his name in, and was most proud of his work in, scientific management; however, he made his fortune patenting steel - process improvements. Taylor was also an athlete who competed nationally in tennis and golf.
ground_truth: Juan Manuel Santos
sub_queries: who declated the American frontier "closed" in 1893? Answer: Frederick Jackson Turner
Frederick Jackson Turner >> employer Answer: Harvard
What Columbia President went to Harvard ? Answer: Juan Manuel Santos