Allen Carl Guelzo (born 1953) is an American historian who serves as Senior Research Scholar in the Council of the Humanities and Director of the Initiative on Politics and Statesmanship in the James Madison Program at Princeton University.
Rachel A. Shelden wrote that for two decades, Guelzo "has been at the forefront of Civil War–era scholarship. In particular, he has focused his analytical efforts on the life and legacy of Abraham Lincoln, publishing books covering the Lincoln-Douglas debates, the origins of the Emancipation Proclamation, and Lincoln's presidential leadership, among others."
Source: Allen C. Guelzo on Wikipedia.