The letters and papers in this collection relate primarily to the period of Polke's life from the time he moved to Northern Indiana upon becoming a commissioner for the Michigan Road to his death with special emphasis on the removal of the Potawatomi Indians from Indiana and the building of the Michigan Road. Some of the manuscripts on the Indian removal have been printed in the Indiana Magazine of History, XLIV: 396-408, December 1948, and XLV: 56-80, 286-288, March and September 1949.

The collection also contains letters and papers concerning Polke's own business affairs, the sale of lands in Northern Indiana, the establishment of the town of Plymouth, Indiana, of which Polke was a proprietor, and the conduct of the Fort Wayne land office.

For the period before Polke became associated with the Michigan Road the collection contains some scattered papers. Manuscripts included from the time of his death in 1843 to 1868 consist largely of family correspondence.

Among the papers in the collection are surveyor's field notes kept by William Polke and his son, Adam Guthrie Polke, 1830-1832; a diary of William Polke, 1831; part of a letter copybook of his, 1834-1841; muster and payrolls of Captain Nicholas D. Gover's company of Indiana mounted volunteers, 1838; a record of state, county, and road taxes for Fulton County, Indiana, 1838; plat maps of Winamac, Indiana, 1839, Birmingham, Indiana, and Plymouth, Indiana; a copy of a letter from Polke to the editors of the National Intelligencer, February 13, 1840, giving an account of the Battle of Tippecanoe; part of an account by Polke of his Indian captivity, which was published in the Fort Wayne Times and the Logansport Telegraph in 1842 and in the Indiana Magazine of History, X: 95-112, June 1913; a copy of an undated account of an overland journey from LaPorte County, Indiana to Oregon in 1847 by John Winchell Cullen, stepson of Adam Guthrie Polke, who lost his life on the journey; a photograph of Delilah (Polke) Gill, (Mrs. James Gill), eldest daughter of William and Sarah (Cooper) Polke; and one of Lucien Lasselle, son of Hyacinth and Nancy (Polke) Lasselle.

Among the correspondents represented in the collection are John Bell, James Blair, Jacob Burnet, Alexis Coquillard, James Currin, John Brown Dillon, John Dumont, John B. Duret, John Hay Farnham, Calvin Fletcher, Allen Hamilton, Edward Allen Hannegan, Samuel Henderson, William Hendricks, Jacob Hull, George M. Jerolaman, Daniel Kelso, James Franklin Doughty Lanier, Hyacinth Lasselle, Isaac McCoy, Samuel Merrill, Samuel Milroy, Austin W. Morris, Morris Morris, John Barron Niles, Joseph Orr, Nathan B. Palmer, Benjamin Parke, Abel C. Pepper, Benjamin Marie Petit, Robert Tyler Polke, Thomas Posey, Erasmus Powell, Thomas Robb, John Sering, William Sheets, Thomas C. Slaughter, Oliver Hampton Smith, Thomas Speed, Cyrus Taber, Waller Taylor, John Tipton, John Walker, Johson Watts, W. G. Wharton, James Whitcomb, Albert Smith White, Joseph Livingston White, and J. Wilson.