| 1 | C&A | Alton R.R. | 4/1938-7/1954 | NAKINA | |
| 2 | C&A | The Chicago and Alton R.R. Co. (The Alton R.R. Co.) | 7/1932-7/1936 | NAKINA | |
| 3 | C&A | The Chicago and Alton R.R. Co. | 8/1920-7/1930 | NAKINA | |
| 4 | C&A | The Chicago and Alton R.R. Co. | 23-Jul | NRHS | |
| 5 | C&A | Alton R.R. | 4/38-1/52 | NRHS | |
| 6 | C&A | CHICAGO & ALTON RR OR ALTON RR | PWRC | ||
| 7 | C&C | Coal & Coke Ry. | 8/1920 | NAKINA | |
| 8 | C&C | *CARTHAGE & COPENHAGEN RAILROAD | PWRC | ||
| 9 | C&C | *COAL & COKE RWY. | PWRC | ||
| 10 | C&C | *COLUMBIA & COWLITZ RAILWAY COMPANY | PWRC | ||
| 11 | C&CA | Canton & Carthage R.R. | 4/1938-4/1961 | NAKINA | |
| 12 | C&CA | Canton & Carthage R.R. | 4/38-4/61 | NRHS | |
| 13 | C&CA | CANTON & CARTHAGE RAILROAD | PWRC | ||
| 14 | C&EI | Chicago & Eastern Illinois R.R. | 10/1957-10/1966 | NAKINA | |
| 15 | C&EI | Chicago & Eastern Illinois Ry. Co. | 8/1920-/1954 | NAKINA | |
| 16 | C&EI | Chicago & Eastern Illinois Ry. Co. | 23-Jul | NRHS | |
| 17 | C&EI | Chicago & Eastern Illinois R.R. | 4/38-10/66 | NRHS | |
| 18 | C&EI | UP [MISSOURI PACIFIC] [CHICAGO & EASTERN ILLINOIS RY] | PWRC | ||
| 19 | C&G | Columbus & Greenville Ry. Co. | 7/1930-10/1966 | NAKINA | |
| 20 | C&G | Columbus & Greenville R.R. Co. | 7/1923 | NAKINA | |
| 21 | C&G | Columbus & Greenville R.R. Co. | 23-Jul | NRHS | |
| 22 | C&G | Columbus & Greenville Ry. Co. | 4/38-10/66 | NRHS | |
| 23 | C&G | COLUMBUS & GREENVILLE RY | PWRC | ||
| 24 | C&I | CAMBRIA & INDIANA RAILROAD COMPANY | PWRC | ||
| 25 | C&IC | Cedar Rapids and Iowa City Ry. | 7/1923-7/1936 | NAKINA | |
| 26 | C&IC | Cedar Rapids and Iowa City Ry. | 23-Jul | NRHS | |
| 27 | C&IC | CEDAR RAPIDS & IOWA CITY RWY. | PWRC | ||
| 28 | C&IM | Chicago & Illinois Midland Ry. | 4/1938-1/1952 | NAKINA | |
| 29 | C&IM | Chicago & Illinois Midland Ry. Co. | 8/1920-7/1936 | NAKINA | |
| 30 | C&IM | Chicago & Illinois Midland Ry. Co. | 23-Jul | NRHS | |
| 31 | C&IM | Chicago & Illinois Midland Ry. | 4/38-1/52 | NRHS | |
| 32 | C&IM | CHICAGO & MIDLAND RWY. CO. (OUT OF EXISTENCE) | PWRC | ||
| 33 | C&IW | Chicago & Illinois Western R.R. | 7/1935-1/1952 | NAKINA | |
| 34 | C&IW | Chicago & Illinois Western R.R. | 4/38-1/52 | NRHS | |
| 35 | C&IW | CHICAGO & ILLINOIS WESTERN RAILROAD | PWRC | ||
| 36 | C&L | Cornwall & Lebanon R.R. (Penna. R.R.) | 7/1930 | NAKINA | |
| 37 | C&L | Cornwall & Lebanon R.R. (Penna. R.R. System) | 8/1920-7/1923 | NAKINA | |
| 38 | C&L | Cornwall & Lebanon R.R. (Penna. R.R. System) | 23-Jul | NRHS | |
| 39 | C&L | PENNSYLVANIA RAILROAD [CORNWALL & LEBANON RAILROAD] | PWRC | ||
| 40 | C&LS | CHICAGO & LAKE SUPERIOR RWY | PWRC | ||
| 41 | C&M | Cumberland & Manchester R.R. Co. (Louisville & Nashville R.R. Co.) | 7/1930-7/1936 | NAKINA | |
| 42 | C&M | LOUISVILLE & NASHVILLE rAILROAD [CUMBERLAND & MANCHESTER RAILROAD CO.] | PWRC | ||
| 43 | C&NW | UP [CHICAGO & NORTH WESTERN TRANS CO] [CHICAGO & NORTH WESTERN RWY.] | PWRC | ||
| 44 | C&O | Chesapeake & Ohio Ry. | 4/1938-10/1966 | NAKINA | |
| 45 | C&O | Chesapeake & Ohio Ry. Co. | 7/1930-7/1936 | NAKINA | |
| 46 | C&O | C. & O. Lines (C. & O. Ry.) | 7/1923 | NAKINA | |
| 47 | C&O | C. & O. Lines (C. & O. Ry.) | 23-Jul | NRHS | |
| 48 | C&O | Chesapeake & Ohio Ry. | 4/38-10/66 | NRHS | |
| 49 | C&O | CSX TRANSPORTATION, INC. [CHESAPEAKE & OHIO RY] | PWRC | ||
| 50 | C&PA | Cumberland & Pennsylvania R.R. Co. | 8/1920-7/1936 | NAKINA | |
| 51 | C&PA | Cumberland & Pennsylvania R.R. Co. | 23-Jul | NRHS | |
| 52 | C&PA | CUMBERLAND & PENNSYLVANIA RAILROAD CO. | PWRC | ||
| 53 | C&S | Colorado & Southern Ry. | 4/1938-10/1966 | NAKINA | |
| 54 | C&S | Colorado & Southern Ry. Co. | 8/1920-7/1936 | NAKINA | |
| 55 | C&S | Colorado & Southern Ry. Co. | 23-Jul | NRHS | |
| 56 | C&S | Colorado & Southern Ry. | 4/38-10/66 | NRHS | |
| 57 | C&S | BNSF [BURLINGTON NORTHERN RAILROAD CO; COLORADO & SOUTHERN] | PWRC | ||
| 58 | C&SE | Colorado & Southeastern R.R. | 4/1938-7/1954 | NAKINA | |
| 59 | C&SE | Colorado & South-Eastern R.R. Co. | 7/1930-7/1936 | NAKINA | |
| 60 | C&SE | Colorado & Southeastern R.R. Co. | 7/1923 | NAKINA | |
| 61 | C&SE | Colorado & Southeastern R.R. Co. | 23-Jul | NRHS | |
| 62 | C&SE | Colorado & Southeastern R.R. | 4/38-1/52 | NRHS | |
| 63 | C&SE | COLORADO & SOUTHEASTERN RAILROAD CO. | PWRC | ||
| 64 | C&T | CATSKILL & TANNERSVILLE RAILROAD | PWRC | ||
| 65 | C&WC | Charleston & Western Carolina Ry. Co. (Atlantic Coast Line R.R. Co.) | 10/1966 | NAKINA | |
| 66 | C&WC | Charleston & Western Carolina R.R. | 4/1938-7/1965 | NAKINA | |
| 67 | C&WC | Charleston & Western Carolina Ry. Co. | 8/1920-7/1936 | NAKINA | |
| 68 | C&WC | Charleston & Western Carolina Ry. Co. | 23-Jul | NRHS | |
| 69 | C&WC | Charleston & Western Carolina R.R. | 4/38-7/65 | NRHS | |
| 70 | C&WC | Charleston & Western Carolina Ry. Co. (Atlantic Coast Line R.R. Co.) | Oct-66 | NRHS | |
| 71 | C&WC | ATLANTIC COAST LINE RAILROAD CO.[CHARLESTON & WESTERN CAROLINA RWY. CO.] | PWRC | ||
| 72 | C&WI | Chicago & Western Indiana R.R. Co. | 8/1920-7/1936 | NAKINA | |
| 73 | C&WI | Chicago & Western Indiana R.R. Co. | 23-Jul | NRHS | |
| 74 | C&WI | CHICAGO & WESTERN INDIANA RAILROAD CO. | PWRC | ||
| 75 | C2C | c2c Rail (former LTS Rail Ltd.) | 1999: 128km standard gauge, electrified at 25kV 50Hz c2c is a train operating company that provides train services, on a franchise basis, on the London, Tilbury & Southend line from Fenchurch Street in the City of London to East London and the entire length of the northern Thames Gateway area including Basildon, Chafford Hundred (for Lakeside), Tilbury and Southend. | GB | TRAFFIC |
| 76 | C760 | Club 760 | A | TRAFFIC | |
| 77 | CA | Chesapeake & Albemarie R.R. Co., Inc. | added 7/1990; 1/1994; eliminated 7/1996; 7/2000-7/2005 | NAKINA | |
| 78 | CA | Chesapeake & Albemarie R.R. Co., Inc. | added 7/90; 1/94; eliminated 7/96; 7/2000 | NRHS | |
| 79 | CA | CHESAPEAKE & ALBEMARLE RAILROAD CO. | PWRC | ||
| 80 | CA | Chesapeake and Albemarle Railroad | RSRV | ||
| 81 | CA | CHESAPEAKE & ALBEMARLE | SCAC4 | ||
| 82 | CA&D | CHICAGO AURORA & DeKALB RR | PWRC | ||
| 83 | CA&S | CHICAGO ATTICA & SOUTHERN RR | PWRC | ||
| 84 | CAA | Atlantic Southeast Airlines | ICAO1 | ||
| 85 | CAAB | CATALANO BROS INC | SCAC3 | ||
| 86 | CAAB | CATALANO BROS INC | SCAC4 | ||
| 87 | CAAC | CLASSIC TRANSPORTATION INC | SCAC3 | ||
| 88 | CAAD | CANADIAN PROPELLER LTD | SCAC4 | ||
| 89 | CAAE | CAMPBELL'S AUTO EXPRESS | SCAC3 | ||
| 90 | CAAE | CAMPBELLS AUTO EXPRESS | SCAC4 | ||
| 91 | CAAH | CALIFORNIA AND HAWAIIAN SUGAR COMPA | SCAC3 | ||
| 92 | CAAH | COULSON AIRCRANE LTD | SCAC4 | ||
| 93 | CAAI | CALDERON AIR TRANSPORT INC | SCAC3 | ||
| 94 | CAAJ | CALARCO INC | SCAC3 | ||
| 95 | CAAK | CAAMANO TRUCKING | SCAC3 | ||
| 96 | CAAK | CALEDON BOATWORKS | SCAC4 | ||
| 97 | CAAL | CANADIAN | SCAC4 | ||
| 98 | CAAM | C & A MOTOR EXPRESS CO | SCAC3 | ||
| 99 | CAAM | CAN/AM | SCAC4 | ||
| 100 | CAAN | CAL-ATLANTIC NORTH AMERICA | SCAC3 |