The Sixth Amendment refers to:
"an impartial jury of the state and district wherein the crime shall have been committed, which district shall have been previously ascertained by law"
Presumably this originally applied to federal offenses and the "districts" were federal judicial districts. Later the Fourteenth Amendment was construed as applying to the states as much as to the federal government. Would that mean "districts" could mean districts within which the courts of a state have jurisdiction?