Short answers, pulled from the story.
William McKinley was the 25th president of the United States, serving from the 4th of March 1897 until his death on the 14th of September 1901. He was a Republican from Canton, Ohio, who won two presidential elections against William Jennings Bryan and led the country during the Spanish-American War of 1898.
Leon Czolgosz, an anarchist, shot McKinley twice in the abdomen on the 6th of September 1901 at the Temple of Music during the Pan-American Exposition in Buffalo, New York. Czolgosz had been inspired by a speech from anarchist Emma Goldman in Cleveland and believed his act would advance the anarchist cause. McKinley died eight days later, on the 14th of September 1901.
McKinley oversaw the annexation of Hawaii in 1898 via the Newlands Resolution and, through the Treaty of Paris signed on the 18th of December 1898, acquired Puerto Rico, Guam, and the Philippines from Spain following the Spanish-American War. His administration also partitioned the Samoan Islands with Britain and Germany, acquiring what is now American Samoa.
The McKinley Tariff of 1890 was a protective tariff that McKinley guided through Congress as chairman of the House Ways and Means Committee. It imposed tariffs on foreign goods to shield American manufacturers from competition. The tariff became a major campaign issue and contributed to McKinley's defeat in the 1890 congressional election, where he lost by 300 votes after the Democrats gerrymandered his district.
During the 1896 presidential election, McKinley declined to campaign by train as his opponent William Jennings Bryan did, instead staying at his home in Canton, Ohio, and receiving delegations of voters on his front porch. Railroads subsidized the excursion rates so heavily that visiting Canton was described as cheaper than staying home. McKinley won the election on the 3rd of November 1896 with 51% of the vote.
McKinley enlisted as a private in the Poland Guards in June 1861 and served in the 23rd Ohio Infantry, fighting at Carnifex Ferry, South Mountain, Antietam, Cloyd's Mountain, Cedar Creek, and other engagements. He rose from private to brevet major, making him the only president who began his Civil War service as an enlisted man and ended it at that rank. He served until the Veterans Corps was mustered out in July 1865.