It's too late for me to avoid this glitch this playthrough, but I decided to create this thread to warn other players about it.
If you visit the Lincoln Memorial before starting the Scientific Pursuits quest then when talking to Dr.Li you'll only be able to say that you've been there and he wasn't there. Which does something to mess up getting the achievement. It doesn't mess up anything in the game, you can still finish the quest, but you'll notice you don't get the achievement.
Thanks for the heads up.
It wasn't the Lincoln Memorial your Dad went to, it was the Jefferson Memorial.
My bad.