The three biggest land gains in U.S. history were made under Grant (Alaska, aka "Seward's Folly"), Jefferson (The Louisiana Purchase), and Polk (Texas, California, "New Mexico").
Yet Polk is number 50 (compare to Grant at 12 and TJ at 3). Sigh.
If it weren't for Polk, the entire Southwest would be equivalent to a third-world nation, swarming with Mexicans...Uh, wait a minute....