May 1866

Wednesday 02:

Peruvian defenders fight off Spanish fleet at the Battle of Callao.

Wednesday 16:

Charles Elmer Hires invents root beer.

Thursday 31:

In the Fenian Invasion of Canada, John O'Neill leads 850 Fenian raiders across the Niagara River at Buffalo, New York/Fort Erie, Ontario, as part of an effort to free Ireland from the English. Canadian militia and British regulars repulse the invaders in over the next three days, at a cost of 9 dead and 38 wounded to the Fenian's 19 dead and about 17 wounded.