Who reigned as King of Prussia and German emperor from 1888 to 1918?

Alfonso XIII was king of which country from 1886 to 1931? Which German engineer, a rival of Karl Benz, built a four-wheeled motor car in 1886? The 1887 Michelson-Morley experiment demolished the idea of which medium that supposedly carried light waves? Which 1888 Rudyard Kipling story is about two adventurers who become kings in Kafiristan? Which 1889 Mark Twain novel sends a 19th-century American back to Camelot? Which 1889 disaster killed over 2,200 people in Pennsylvania when the South Fork Dam failed? Which artist painted "The Starry Night" in 1889 and died in 1890? In July 1890, which territory, now famous for its potatoes, joined the Union as the 43rd state?