Idaho has just two congressional districts and the border between them has been shifting on a steadily westward march since the 1970s as the population of Boise grows.
When the state's bipartisan citizen redistricting commission looked at redrawing the lines in 2011, some members pushed to place all of Ada County and Boise in the 1st Congressional District, shifting Canyon County to the 2nd District.
But that would have resulted in about 400,000 of Idaho's 1.5 million people voting in a new district -- a move the committee found ultimately too radical.
Instead, they chose landmarks like the Boise River and State Highway 55 to mark the new borders, shifting more Democratic voters into the 2nd District.
Still, in the highly Republican state of Idaho, the shift had little impact.
Dean Ferguson, spokesman for the Idaho Democratic Party, says the 1st District, with its liberal strongholds in Moscow and some Boise neighborhoods, is still considered a potential win for Democrats, and the 2nd District remains much tougher.