“interstate” = everything but that which is confined to one state
Gibbons
a.  anything that crosses state lines
b.  everything except completely internal commerce
c.  navigable waters Daniel Ball  [note:  Brazos River that law
school on = navigable]
d.  if final destination is in stream of interstate commerce => all
trips are interstate as to that item
e.  rule:  first leg & last leg of many-legged trip are not
interstate (Josh airport ex)