Jefferson County in Alabama has filed the biggest municipal bankruptcy in U.S. history after failing to refinance nearly $4 billion in debt. Jefferson County was mired in debt after reaching a complicated scheme with Wall Street investors to finance the cost of rebuilding a broken sewer system. The county reached an agreement with the Wall Street giant JPMorgan to refinance through interest rate swaps, but later sued the firm after its debt ballooned on what was initially a $250 million project.