Polarization of Congressional districts is a threat to our democracy as respect for Congress diminishes.
Congressional districts are only required to be contiguous. This definition of contiguous is severely abused.
By requiring Congressional districts to adhere to county boundaries districts would consist of one or more entire counties. This would prevent political parties from drawing boundaries based entirely on the demographics of specific population. It would force representatives to represent a broader cross-section of citizens.
As data-mining techniques become more effective, gerrymandering will become increasingly effective polarizing the country further and threatening our democracy. This would not end, but would set a natural limit to the efficacy of gerrymandering.