How did the C&O get to the Chicago Loop?

From what I can tell, the C&O came into Griffith, Indiana from the southeast, between the Erie and GTW, and crossed everything at that junction. From there it ran northwest just west of the Erie line. Then the trail runs cold when the Erie and Monon start to parallel. Where did the C&O run in relation to those two, and how did it get through State Line Junction? Then how did it run from there? July 2003 Trains shows it running to "Louisville Junction" around Burnham, and then running north on either the C&WI of the Nickel Plate to Pullman Junction, where it continued along the NKP and IC to Central Station. Can someone help fill in the blanks here? Also, did it always use Central Station? Thanks for any help.

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As a related question (since the C&O took it over), how did the Pere Marquette get there? The end of PM trackage in Porter is at a junction with two NYC lines, but somehow it got to the B&OCT in South Chicago.

When the C&O took over the Pere Marquette, did that have any effect on the Chicago entrance of the two companies?

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Looks like http://hometown.aol.com/chirailfan/routegcs.html gives the answer for the Pere Marquette - it switched to the B&O at Pine Junction. The map at http://www.railsandtrails.com/Maps/Chicago/index.htm shows the connector track it likely used, merging with the B&O just northwest of the split for the B&O/PRR line west to State Line Junction.

http://hometown.aol.com/chirailfan/routedea.html puts the C&O in Dearborn Station. Was that a later change, or is the July 2003 Trains wrong about the 1928 C&O routing? How did the later connection work at State Line? Did the C&O merge with one of the other lines prior to the junction?

The C&O thru griffith was sometimes refered to as the C&O of Indiana...the line at griffith tied onto the EL main there and the EL and C&O ran together till state line tower was reached at that point the rails belonged to the chicago and western indiana..both railroad used the C&wi to access chicago innerchanges the line thru griffith in C&O days was freight only..the C&Oleased a small yard near BRC clearning yard it was where all freight terminated...the passenger traffic on the PM side tied onto the NYC at porter tower and at pine jct there was a connecting track to the old B&O main to chicago..(NOT B&OCT) the B&OCT connection was for freight only while the former B&O pass main ran next to the NYC main all the way thru the east side up to the river bridge there at Rock Island jct the passenger traffic used the RI south chgo branch thru gresham jct to braniard jct there they entered B&O rails once again for the trip toward the city the C&O passenger trains shared Grand Central Station with the B&O and SOO line ...hope this helps

That doesn't really help, but I've gotten information elsewhere that does help. Here's what I have:

Chicago, Cincinnati and Louisville Railroad chartered 11/1/1866 as
reorganization of Cincinnati, Peru and Chicago Railroad. Built from
Peru to La Porte, and the Indianapolis, La Porte and Michigan City
Railroad continued from La Porte to Michigan City. Plans were to use
the Lake Shore and Michigan Southern Railway from La Porte to Chicago;
not clear if it did. If it used the Pere Marquette it would have
joined in Michigan City. Not sure where it would have joined the Monon
if it ever used that; maybe that was on the later alignment from Hammond.

Cincinnati and Indiana Western Railroad and Cincinnati, Richmond and
Muncie Railroad chartered in Ohio and Indiana to build the line
between Cincinnati and Griffith (the junction with the Erie
southeast of Hammond). Both consolidated with the CC&L 6/1/1903. Once
completed, terminated at Hammond (or Griffith?) for several years.

Hammond Belt Railway chartered 1906 in Illinois and opened 4/6/1907
(?), from the CC&I in Hammond (which crossed the Erie and everything
else at Griffith and ran parallel to the Erie to south of the
Michigan Central Railroad crossing) west and northwest to the Indiana
Harbor Belt Railroad at Louisville Junction. (The 1913 map does a
great job of showing the line; short parts of grading can be seen on
topo maps.) Ran over the IHB to Dolton, then over the CC&I's own track
from just wets of Dolton to the IC just south of Riverdale, then over
the IC to Central Station.

Reorganized 7/6/1910 as Chesapeake and Ohio Railway of Indiana.
12/1/1910 began using the Erie from Hammond to State Line and the C&WI
to Dearborn. 3/1/1925 began using the Nickel Plate from a connecting
track somewhere between the Michigan Central crossing and State Line
to the IC south of Grand Crossing (connecting track shown on
http://70.121.38.224/Chicago%20Division/jpegs/113.jpg ) and the IC to
Central Station.

By 1945, service was cut back to Hammond, with transfers advertised to
the Monon, Erie or South Shore. Later stopped running altogether.

Ok this much I can tell you..I worked at griffith tower in the late 70,s..so if you are looking for older info i cant help..but...from what i was told the C&O actually owned one track and the EL the other but both railroads used them as a double track line....the line joined so to spreak at GRIFFITH tower and ran thru Hammond to HY tower near 165th st. the tracks ran together on a very wide sepration..at HY tower one of the tracks not sure if it was the old C&O or old Erle made a "s" curve the two tracks joined at HY tower where there was crossovers each way ..at one time the C&O made a swing back to the west crossed the ERIE and the MONON not far from the monons 173rd st yard continued on across stateline road from the the trail gets lost but there are a couple old signs along stateline road that say"C&O property no tresspassing" to this day once the C&O was realined they ran over the erie thru HAMMOND yard and on to STATE LINE tower where the C&WI was accessed...at one time the C&O used the NKP's calumet yard for freight of this line but later leased ROCKWELL st yard from the BRC....

TrainmasterTim is correct. The Erie and C&O each owned a track west of Griffith, but it was controlled and maintained by the Erie. The C&O actually ended at HY, and trains continued to Rockwell. IIRC from what I was told and read, a couple trains went directly to the NKP or the Belt for forwarding, since the C&O didn't maintain a large presence in Chicago.
Same from the PM standpoint, just alot of handing off.