After half a century of teaching and with two Pulitzer Prizes under his belt, Warren Professor of American History David H. Donald is poised to complete the most challenging project of his career.

Harvard's preeminent scholar of 19th-century American political history will retire this June after an 18-year tenure at the University. And as he ends one part of his scholarly duties, Donald prepares to devote his full attention to an unprecedented analysis of the figure whose life and ideas his previous research had only begun to examine.

"I spent most of my life not doing a life of Abraham Lincoln," Donald says. "Most of my earlier work was around the periphery of Lincoln. It's a very large and complex issue that I was not sure I should tackle."

Yet in 1993, Donald says, he hopes to release a definitive biography of the nation's 16th president published by Simon & Schuster. He has received a generous grant from the National Endowment for the Humanities to help fund the needed research along the way.

"I'm not retiring to play golf," says Donald who will turn 71 this October. "I'm retiring to spend my full time on research and writing."

Donald's colleagues at Harvard have praised his latest research efforts for their groundbreaking insight into this era of American history.

"Donald is a demonstrably great biographer," says Winthrop Professor of History Stephen A. Thernstrom, referring to the scholar's two previous biographies which won Pulitzer Prizes in 1961 and 1987.

And Warren Professor of American History Ernest R. May shares Thernstrom's sentiments: "I'm sure it will be extraordinary. Donald is very sensitive to interpretations of periods and people. I expect this to be a remarkable book."

Breaking New Ground

Unlike many of the Lincoln biographies that have come before, Donald's endeavor will use extensive materials from the former president's personal papers that were sealed until 1947.

"Lincoln's personal papers which he received as president were sealed off after his death by his only surviving son, Robert Todd Lincoln," Donald says. "Only two biographies published in 1890 were allowed to look at these papers, and these were biased biographies."

Since 1890, several other scholars have written about Lincoln, notably Carl Sandburg and James G. Randall, in the earlier part of this century. But, Donald says, they did not have access to a number of personal documents.

"There has never been a modern life of Lincoln that had full access to the President's private papers," the Harvard scholar says.

And fellow American historian Thernstrom says Donald has picked an appropriate time to work on the Lincoln project. "It will give us a new vantage point for the 1990s," he says.

"The time is ripe for a full Lincoln biography," says Thernstrom. "Lincoln is a fascinating figure of momentous importance, and there hasn't been a serious biography of him for 30 years."