When municipal officials want to build for the future, they have a powerful financial tool at their disposal: general obligation bonds that yield millions of borrowed dollars. The money is meant to let cities move forward on costly projects that will serve the community for decades.

But in an unprecedented analysis of Chicago’s finances, a Tribune investigation found that city officials have long abused their borrowing privileges, spending funds meant for long-term initiatives on problematic short-term expenses from library books to legal settlements.

Residents know little about it, as Illinois law doesn’t require Chicago to ask voters’ permission before issuing bonds. And when the city can’t pay what it owes, it uses yet more borrowed money as leverage to push off payments on old bonds.

This pattern of fiscal recklessness, which started under former Mayor Richard M. Daley, created a mountain of debt that threatens the financial future of the city. Now Rahm Emanuel is groping for ways to deal with the problem along with a looming pension crisis and chronic budget deficits.