Interstate 69 is currently a rather short road, going from the
canadian border of
Michigan to
I-465, the freeway loop around
Indianapolis.
The US department of transportation has proposed I-69 as the designation for the future NAFTA Super Highway, which will connect Canada to Mexico, starting at its current location, extending down through Houston and ending at Brownsville or Laredo.
Because I-69 will then be a long North-South interstate that doesn't end in a 5, this is bound to give road-geeks indigestion.
Personally, I'm more worried about sign theft.