Answer: To make sure the Union Army could not use Confederate resources.
Step-by-step explanation:
On Evacuation Sunday (April 2, 1865), President Davis, his Cabinet, and the Confederate guardians left Richmond and escaped south on the last clear railroad, the Richmond and Danville. The retreating troops were following orders to set fire to bridges, the armory, and sheds with supplies as they fled, to make them useless for the Federalists. Union troops put out the flames.