Business US-6 in NW Indiana is as follows:
I-80/94 at US-41(Indianapolis Blvd) South along US-41 to Ridge Rd (Former US-6) East via Ridge Rd thru Highland,Griffith, Gary, Lake Station and Hobart to US-6/IN-51 (Ripley Street). This was approved by AASHO/AASHTO in the early 60's. I have lived in NW Indiana all my life and this has been an interesting route to try and find history on. Somewhere, I have a copy of the actual application from AASHTO showing this change.
Also of note:
US-12 reroute:
In Gary it used to follow the Industrial Hwy(By the Gary/Chicago Airport) from Bridge St NW to IN-912/US-12 Columbus Dr
Now, it multiplexes with US-20 from Bridge St Westerly to IN-912 then, North along IN-912 to Columbus Dr then it proceeds West into East Chicago.
Take Care,
Stephen