Track Elevation Map, 1908
Excerpt of the Track Elevation Department map showing the various railroads in the Bridgeport area.

The dates shown refer to the the city ordinances requiring the railroads to raise their tracks above street level. The first track elevations in Chicago were done in 1892, which were those of the Illinois Central railroad for the World's Fair. A general ordinance followed in 1893, whereafter ordinances were passed for specific sections of track.

The purpose was for safety as well as to eradicate the delays caused by stopped trains (or by those making switching maneuvers). Track elevation was deemed more practical than building viaducts, since viaducts required approach space for the incline of the road, whereas with a raised railroad bed, only a few feet of clearance was needed for embankments or walls.

Red colored lines on the map indicate completed elevations; blue, under construction; and green, those projects yet to commence. Today similar policies are referred to as separation of grade improvements. Metra commuter rail currently has a policy seeking to eliminate grade crossings on its routes. Few grade crossings, however, have been eliminated. Outer sections of the city of Chicago and the suburbs have not yet been able to obtain what the older sections of the city had since the early 1900s.

Source: Plate II, Track Elevation Department, Track Elevation Within the Corporate Limits of the City of Chicago: to December, 1908 (Chicago: City of Chicago, 1909).