The first president with facial hair was Lincoln, the last TR. The last serious candidate was Dewey. Mrs. Longworth’s comment that he looked like the groom on a wedding cake put that fashion finally in the tomb.

American facial hair fashions track British facial hair fashions. I have seen the mid-nineteenth century fashion for facial hair attributed to the Crimean War, when officers could not shave for extended periods (why? did their razor blades corrode in the Black Sea air? Was it easier to shave during the Peninsular campaigns?). Another explanation is that Englishmen grow facial hair when they have reigning Queens (William III does not count). Elizabeth I gave us many sleek sinister staches and goatees, Victoria ruled over beavers and full sideburns, Elizabeth II coincided with the Beatles in their Sgt. Pepper phase. I am not familiar with the hairiness or otherwise of the reign of Queen Anne. This theory too has some holes in it, since hairiness has not extended throughout the reign of the current Queen. Maybe it Prince Charles had a stiff spiky beard he would be less fatally attractive to women.