How Lincoln and an ambitious postmaster general gave us today's shutdown

The current federal government shutdown, like all previous ones in the last century, was caused by an obscure law called the Anti-Deficiency Act.

The law prohibits federal agencies from spending money that Congress hasn’t specifically appropriated and exists to prevent the president or agency heads from writing hot checks. The law was codified in 1905, but provisions of it date almost to the nation’s founding, as it developed from the long-running struggle between the executive branch and Congress over control of federal spending.