So... just when exactly did the Lindsey Creek Bypass (later aka I-185) get built/opened? Here seems to be the start of it all, but how long it took seems to be still obscure documentation... online, at least:

1,500 Mile Interstate Additions Added per 1968 Federal-Aid Highway Act
State - Chief Route Number - Description - Length (Miles)- 1968 Cost
Georgia - I-185 - Columbus spur - 38.8 - 32.6

Now we know that the Lindsey Creek Bypass didn't go past Airport Thruway until late 1979, but it seems to have definitely been a part of the 1968 act detailed below... so when did construction begin on the Lindsey Creek Bypass? Seems not long after 1968 would be logical, but how long, months? Years?

Additions to the Interstate System Segments Added on 12/13/68 in Accordance with 1968 Highway Act
•Section 14 of the Federal-Aid Highway Act of 1968 (P.L. 90-495) modified Title 23 by adding the following paragraph to Section 103(e)...
"(3) In addition to the mileage authorized by paragraphs (1) and (2) of this subsection, there is hereby authorized additional mileage of not to exceed 1,500 miles for the designation of routes in the same manner as set forth in paragraph (1), in order to improve the efficiency and service of the Interstate System to better accomplish the purposes of that System."

http://www.fhwa.dot.gov/highwayhistory/data/p...

Part I - History - Engineering Data - Highway History - FHWA
www.fhwa.dot.gov
In 1998, with the Interstate System essentially complete, FHWA's Office of Engineering compiled information about development of the program.