Writing is thinking. To write well is to think clearly. That's why it's so hard." (Interview with NEH chairman Bruce Cole, Humanities, July/Aug. 2002, Vol. 23/No. 4)

In December 2012 Allegheny County Pennsylvania announced that it would rename the 16th Street Bridge in Pittsburgh in honor of McCullough. " He started it as a book about the founding fathers and back-to-back presidents John Adams and Thomas Jefferson; but dropped Jefferson to focus on Adams. In 2003 the National Endowment for the Humanities selected McCullough for the Jefferson Lecture the U.

McCullough's two Pulitzer Prize-winning books Truman and John Adams have been adapted by HBO into a TV film and a mini-series respectively. McCullough's most recent history The Greater Journey (2011) is about Americans in Paris from the 1830s to the 1900s.