War of 1812. U.S. declares war on Britain over British interference with American maritime shipping and westward expansion.
Illinois is the 21st state.
English (Lancashire) and Scottish (also northern Ireland): probably a habitational name from any of various minor places named Whiteside, from Old English hwīt ‘white’ + sīde ‘slope (of a hill)’. Reaney, however, quotes early forms without prepositions and derives the surname from a nickname.