It seems to me that if knowledge of Lincoln is the bedrock of popular historical knowledge, as a teacher you can build outward from that central piece of terra firma:
At the start of this fall semester I gave my 160 introductory students a 100-point pretest of what I like to call "walking around" knowledge of American history. I guesstimated that the average score would be somewhere in the low 70s. Instead a lone 74 turned out to be the top score. The average score was 27. Here are a few troubling examples of the results. Not a single student could identify Nathan Hale as having regretted he had only one life to give to his country. Given critics' concerns about the non-mention of the Great Society in an early draft, it might be noteworthy that four students thought Lincoln was its architect, while all of two mentioned Lyndon Johnson.
A whopping (?) 95 did name Lincoln as our Civil War president, while only 52 could pinpoint the 1860s as the decade when the war was fought. Forty-four recognized that Theodore Roosevelt was the "Rough Rider," while 13 knew that Ronald Reagan defeated Jimmy Carter in 1980. Sixty-eight linked the Brown vs. Board of Education decision with school desegregation, and 60 could identify Germany as the primary foe during World War I.