The Sunday LA Times included a feature with a little different twist on usual top or bottom Presidential lists. Historians who have written about great Presidents were asked about the failings of those Presidents, and historians who have written about "failed" Presidents were asked about good things those Presidents did:
Pierce enabled the expansion of slavery in the West. He also secretly plotted to acquire Cuba from Spain. A drinker of some renown, he was referred to derisively as "hero of many a well-fought bottle."
The best thing Pierce did as president had to do with excrement. Specifically, guano, or bird droppings, which were so essential to U.S. agriculture in the mid-1800s that the era is sometimes referred to as the Golden Age of Guano. In 1856, Pierce signed the Guano Island Act, which allowed U.S. citizens to mine guano on any unclaimed island in the world. It was a time of expansion, and what the guano law did was enable the U.S. to claim rights to whatever land it wanted, as long as somebody else didn't already own it. It was a very smart move -- if you like empires.
-- Larry Gara
Author, "The Presidency of Franklin Pierce"