I remember all the hours we spent in 18th Century American History class discussing how the Founders IMMMEDIATELY appointed dozens of full-time Federal prosecutors in every jurisdiction, and how plea bargaining was one of the big subjects of the Federalist/Anti-Federalist papers.
Or not...
Screw the Federal government and its phony "Laws For The Little People".
Federal crimes were probably limited to piracy on the high seas (which would be outside the jurisdiction of any state), and Federal tax evasion.
The U.S. Department of Justice didn't even exist until 1870.