"Altgeld's castles" are buildings in the Gothic Revival style at five Illinois public universities, all built at the initiative or inspiration of Illinois Governor John Peter Altgeld During his term as governor (1893-1897), Altgeld expressed certain opinions on how buildings should be erected in the state of Illinois. In his second biennial message to the state legislature, he discussed how buildings were being constructed without consideration for their outward appearance. He stated that it was time for buildings to become more aesthetically pleasing in addition to being functional, and he suggested the "Tudor-Gothic style" as the most inexpensive way to do this. Consequently, several of the state universities in Illinois erected buildings which resembled castles in his honor. College folklore states that these buildings have aligned corridors and rooms so that they could all be "put together" to create one large building, but there is no evidence to support this rumor.

John Peter Altgeld was an American politician and the 20th Governor of Illinois, serving from 1893 until 1897. He was the first Democrat to govern that state since the 1850s. A leading figure of the Progressive movement, Altgeld signed workplace safety and child labor laws, pardoned three of the men convicted in the Haymarket Affair, and rejected calls in 1894 to break up the Pullman strike by force. In 1896 he was a leader of the progressive wing of the Democratic Party, opposing President Grover Cleveland and the conservative Bourbon Democrats. He was defeated for reelection in 1896 in an intensely fought, bitter campaign.