1913: Pennsylvania Railroad interests incorporated a new railroad to connect Pittsburgh, Cincinnati, Chicago & St. Louis (PCC&STL, or Panhandle) lines that connected the Indianapolis line to Terre Haute to the Terre Haute line to Logansport and South Bend. Part of the reasoning for this was simply the fact that the PRR had no direct line from Indianapolis to Chicago. At the time, PRR trains between those two cities were using trackage rights to Kokomo via the Lake Erie & Western (now known as the Nickle Plate). At Kokomo, PRR tracks would connect to Logansport and Chicago.
Officially created on Christmas Eve, 1913, the Indianapolis & Frankfort would branch off of the Vandalia line just west of what is now Girls School Road. It wouldn’t be until 28 February 1916 that a location was decided upon and construction would begin. After its leaving the Terre Haute line, it would almost immediately cross the National Road. The construction would include quite a few grade separations, mostly overpasses, in Marion County (Morris Street, Rockville Road, 10th Street, 21st Street, Country Club Road and Crawfordsville Road). This was in keeping with the massive projects that were going on all over Marion County elevating railroad tracks. These overpasses would be would be typical PRR concrete arch bridges. Most of these exist today. The bridges over state roads (US 40 [Washington], US 36 [Rockville] and US 136 [Crawfordsville]) have been replaced to allow widening of those roads.
There were also overpasses constructed over the Big Four, Peoria & Eastern and the Baltimore & Ohio, at least in Marion County. The bridges over the old P&E and old B&O still exist, even though the tracks below has long since been abandoned.
The railroad continued at grade until it reached the south side of Lebanon. It would be elevated all the way through the Boone County seat of government. Due to the late construction of this route, there were really only two towns on the entire railroad, those being Lebanon and Frankfort. Most of its 41 miles is rural railroad, crossing through fields and county roads. At Frankfort, it connected to the Logansport-Terre Haute line near what is now South Street.
According to the book “Centennial History of the Pennsylvania Railroad Company 1846-1946,” the I&F would be opened early in 1918, with the entire line in full operation on 16 June 1918. By the end of 1920, the PRR had invested $4,960,000 in the line. This was realized in the PRR ownership of that amount of the stock in the Indianapolis & Frankfort.
In the 1970s and 1980s, with the abandonment of old Pennsylvania Railroad lines around Indianapolis, the I&F was one of the few routes that would remain as part of Conrail. (The other was part of the Louisville Sub, aka the old Madison & Indianapolis. But this would only be to milepost 4, which is at University Heights.) The rails from Union Station west to the I&F cutoff, including the transfer yard at Oliver Street, would be kept in place, with the original Terre Haute line removed west of the cutoff. At the northern end, the tracks exists to just shy of SR 75 north of Frankfort, with the line to Logansport and South Bend removed from that point.
Recommended reading for this post include the above mentioned ” Centennial History of the Pennsylvania Railroad Company 1846-1946,” which has one paragraph dedicated to the Indianapolis & Frankfort on page 542. Another good book concerning the Pennsylvania Railroad in general is “The Pennsylvania Railroad in Indiana” by William J. Watt. (This book has a paper cover that shows the PRR station at Southport on the old M&I.) Both of these books are actually in my personal library of sources.