Matthew Yglesias, responding to this amusing story about a 1930s U.S. plan to invade Canada, notes that Canada was formed in 1867 partly because of fears that Republican leaders in the U.S. would invade Canada to add Republican voters to counteract Democratic votes from soon-to-be rehabilitated South. Actually, the Republicans came up with a better strategy: they divided the Western territories into lots of little states. Support for the Republican party before and during the Civil War was strongest in the Upper Midwest and New England. It would make sense to artificially inflate the number of Senators and electoral votes from Republican-leaning plains states by making more states than the sparse population would otherwise justify.
In 1860, the territories were only Kansas, New Mexico, Utah, Washington, and Nebraska. In the middle of the Civil War, the Republican Congress hastily admitted Nevada to get its electoral votes 8 days before the 1864 election, meanwhile splitting Utah into Utah and Colorado, New Mexico into New Mexico and Arizona, Washington into Washington and Idaho, and Nebraska into Nebraska, Montana, and Dakota. In 1889, Dakota was split into North and South Dakota, again partly due to pressure to increase Republican control of the Senate.
Of course, this backfired on the Republicans, as many of these plains states later went Populist, but that's the way things go. So if you're looking to blame someone for why Wyoming gets one senator per 250,000 people but California gets one senator per 16 million, you can blame post-Civil-War Republicans in addition to the Founding Fathers.