The modern conclusions drawn here are very questionable, but the Civil War history was pretty edifying: I knew that Lincoln had pushed through the statehood for a couple of states, but the political impact had never been fully clear until reading this.

This largely forgotten act of line-drawing enabled one of the most consequential gerrymanders in American history. Because the virtually unpopulated Nevada became its own territory, Republicans could admit it as a state just four years later. That gave the Party of Lincoln two extra seats in the Senate — helping prevent Democrats from simultaneously controlling the White House and both houses of Congress until 1893.

Nor was this selective admission of the Republican state of Nevada an isolated case. Among other things, the reason why there are two Dakotas — despite the fact that both states are so underpopulated that they each only rate a single member of the House of Representatives to this day — is because Republicans won the 1888 election and decided to celebrate by giving themselves four senators instead of just two.

Source: The forgotten history of how Abraham Lincoln helped rig the Senate for Republicans – ThinkProgress