The year around 1900 might be approximate.
Lines involved are generally identified by historic division (Div.), subdivision (SD), district (Dist.), or branch (Br.). Where a branch is identified with a railroad and not a name, it typically might be an industrial spur or another line with an uncertain identity. Some cities had belt railroad lines, whose routes are also uncertain.
Electric street or interurban railways are identified by "elec.", those railways generally are not covered here except where "steam" railroads are also involved. Also noted are certain interlockings involving logging railroads and other railroads which did not survive long.
Some of the more obscure railroads and lines, are described at the bottom of this page.
Several larger cities had multiple interlocking towers. Because of historic inconsistencies in naming of interlockings and other factors, the locations are not always certain.
1887 Ranney CMSP&P C&M SD/C&NW Farm SD 1888 Tower BA (Milwaukee) C&NW Milwaukee Div./CMSP&P Br. Washington Street (Milwaukee) CMSP&P C&M SD/C&NW Madison Div. Allis (Milwaukee) C&NW Milwaukee Div./C&NW Madison Div. 1889 Duplainville CMSP&P La Crosse Div./SOO (WC) 1891 NW Tower (Fond Du Lac) CMSP&P Fond Du Lac SD/C&NW Lake Shore Div. 1892 Camp Douglas CMSP&P La Crosse Div./C&NW (CSPM&O) Medary Jct. CMSP&P La Crosse Div./C&NW Winona SD 1893 Eau Claire Holmes Holmes Logging Ry./CMSP&P Channing Line Grand Crossing (La Crosse) CMSP&P La Crosse Div./CB&Q 1895 Racine Jct. C&NW Milwaukee Div./CMSP&P R&SW Line 1896 Hilbert SOO Manitowoc SD/CMSP&P Plymouth SD Monona Yard (Madison) C&NW Madison SD East Wye/CMSP&P M&P SD Midland Crossing CMSP&P Fond Du Lac SD/SOO (WC) 1897 Central Ave. (Superior) Ashland Jct. C&NW (CSPM&O)/Minneapolis St. Paul & Ashland Railroad (logging) 1899 Valley Jct. C&NW (CSPM&O)/CMSP&P Babcock Br. 1900 Elroy C&NW Madison SD/C&NW (CSPM&O) Winona Jct. CB&Q/C&NW Winona SD 1901 Eau Claire C&NW (CSPM&O) drawbridge Burnham Slip (Milwaukee) CMSP&P drawbridge Rice Lake C&NW (CSPM&O) Itasca SD/SOO Rice Lake Line Madison (Monona Tower) CMSP&P Madison SD/C&NW Madison SD Bardwell CMSP&P Fox Lake SD/CMSP&P R&SW Line Nash C&NW (CSPM&O)/Ashland Siskiwit & Iron River Logging Railroad (logging) Genoa City C&NW Farm SD/C&NW Williams Bay SD 1902 Bancroft C&NW Marshline SD/SOO Portage Line Wisconsin Rapids C&NW Marshline SD/SOO (2 miles north of town) Fond Du Lac CMSP&P Fond Du Lac SD/C&NW Clyman SD Janesville CMSP&P Fox Lake SD/C&NW Janesville Belt Turtle Lake SOO/C&NW (CSPM&O) electric Cameron C&NW (CSPM&O) Itasca SD/SOO 1903/1904 Itasca C&NW (CSPM&O)/NP Chippewa Falls C&NW (CSPM&O) Itasca SD/(CSPM&O)/SOO (WC) Shepherd C&NW (CSPM&O)/Black River Falls Loop Wright (Levis) C&NW (CSPM&O)/Black River Falls Loop Trevino CB&Q/CMSP&P Chippewa Valley Div. Prairie Du Chien (Crawford) CB&Q/CMSP&P Prairie SD Milwaukee (Grand Avenue) CMSP&P Lake Shore Junction (Milwaukee) C&NW Wisconsin Div./C&NW Lake Shore Div.