Steam locomotives with names beginning with O that have operated in North America:
| Name | Railroad, # | Builder, s/n | Build date | Whyte type | Notes |
|---|---|---|---|---|---|
| O. B. Filley | TT 56 | Grant | 10/1882 | 2-6-0 | NG; SG'ed 10/1887; sold 4/1900 to Dilley Foundry Co. |
| O. E. Britt | M&SP 136 | Taunton 474 | 9/1869 | 4-4-0 | Rn #1235 in 1899; sold 12/1901. |
| O. G. Murray | TT 84 | Rhode 1463 | 6/1884 | 2-6-0 | NG; SG'ed 9/1887; sold 5/8/1901 to Griffin Mill Co., Griffin, Arkansas. |
| Oakland | CP 179 | Vulcan 3 | 1863 | 4-2-0 | Ex-SF&O 6/1870; shopped 4/1873 for yard service at Oakland; off roster by 1873. |
| Oakland | NYOW 89 | Rhode 535 | 6/1873 | 4-4-0 | Never delivered to NYOW; sold to Providence & Worcester #30; sold to NYP&B #130; transferred to New Haven #388; rn 1745. |
| Oakland | S&O | Baldwin | 2/1870 | 2-6-0 | Derailed at the same place twice trying to stop for animals on the track in 1871 and 1881. |
| Oaxaca | O&E 4 | Baldwin 20150 | 3/1902 | 2-8-0 | |
| Oberon | GWR 51 | 2-4-0 | Inside connected; 5 ft 6 in gauge until c. 1872. | ||
| Obispo | Pan | Portland | 1854 | 0-4-0 | |
| Ocampo | FCHN 7 | Baldwin 9876 | 3/1889 | 2-8-0 | NG; became NdeM #7 in 1908. |
| Ocmulgee | CR&B | Rogers 48 | 9/1843 | 4-4-0 | |
| Oconee | CR&B | Rogers 24 | 9/1840 | 4-2-0 | |
| Oconomowoc | Mi&W | Niles | 1854 | 4-4-0 | Transferred to LC&M in 1856; became M&SP #41 Minnehaha in 1863; off roster by 1888. |
| Ocotlan | O&E 5 | Baldwin 20149 | 3/1902 | 2-8-0 | |
| Ogdensburg | CP 38 | M & Aldus | 6/1867 | 4-6-0 | Rn 1891 #1528, #1071; s to Crescent City RR #2 2/5/1910. |
| Ogdensburg | O&LC 9 (2nd) | M & Aldus | 1867 | 4-4-0 | Rn 1/1/1891 #309 W. A. Short; Scrapped. |
| Ogdensburgh | NYOW 52 | Baldwin 2929 | 9/1872 | 2-6-0 | Scrapped 10/6/1908. |
| Ogechee | CR&B | Rogers 47 | 8/1843 | 4-4-0 | |
| Oglethorpe (1st) | CR&B | Rogers 21 | 3/1840 | 4-2-0 | |
| Oglethorpe (2nd) | CR&B | Rogers 457 | 1/1854 | 4-4-0 | |
| Oil City | OCRR | 4-4-0 | |||
| Ojuela | MRR | Baldwin 15049 | 9/1896 | 0-4-2T | |
| Old Baldy | D&RG 30 | Baldwin 4382 | 1878 | 2-8-0 | |
| Old Ironsides | PG&N | Baldwin 1 | 11/1832 | 2-2-0 | Traded in to Baldwin by PG&N in 1846. |
| (Old Maude) | B&O 2400 | ALCO | 1903 | 0-6-6-0 | Never officially named by the B&O. |
| Old Rube | D&RG | Baldwin | 2-8-0 | Narrow gauge C-16. | |
| Old Zach | CV 10 | H & Drury | 1848 | 4-4-0 | Rb 7/1854; rb 7/1864; rn 1864 Gen. Taylor; rn 1869 Stanbridge. |
| Olema | NPC 4 | Baldwin 3629 | 1874 | 4-4-0 | Wrecked at Waldo Point 1894; rb; bec NoS #4 1902; bec NWP #4; rn #81; scr 1911. |
| Olive | IRR 6 | Baldwin 1671 | 10/1867 | 0-6-0 | |
| Olomana | WaSC | 0-4-2T | |||
| Olympia | O&CV 3 | Baldwin 7298 | 5/1884 | 2-6-0 | Delivered to Columbia & Puget Sound 5/1891. |
| Omaha | A&P 16 | Rhode 944 | 3/1881 | 4-4-0 | |
| Omaha | UP 8 | Schen | 1865 | ||
| Oneida | NYOW 8 | Rhode 124 | 9/1869 | 4-4-0 | Scrapped 1/18/1887. |
| Oneida | S&U | Rogers 22 | 6/1840 | 4-2-0 | |
| Oneonta | CP 14 | Cooke | 3/1866 | 2-6-0 | Rb 6/24/1871 as 4-4-0; scr 10/6/1899 at Sacramento. |
| Onondaga | NY&E 31 | Rogers 161 | 2/1849 | 4-4-0 | 6 ft gauge. |
| Onondaga | NY&H | Rogers 366 | 1/1853 | 4-4-0 | |
| Onondaga | S&U | Rogers 25 | 10/1840 | 4-2-0 | |
| Ontalaunee | P&R | Newcaslte | 1843 | 4-4-0 | |
| Ontario | CV 3 | Amoskeag | 1851 | 4-4-0 | Rebuilt 8/8/1859; renamed Sheffield before March 1871. |
| Ontario | L&W | Rogers 323 | 6/1852 | 4-6-0 | |
| Ontario | NY&E 32 | Rogers 162 | 2/1849 | 4-4-0 | 6 ft gauge. |
| Ontario | NYOW 22 | Rhode 199 | 8/1870 | 0-4-0 | Leased 1884 to Terminal Co; sold. |
| Ontario (1st) | O&LC 9 (1st) | Souther | 10/1850 | 4-4-0 | |
| Ontario (2nd) | O&LC 17 (2nd) | H & Drury 299 | 4/1851 | 4-4-0 | Ex-Erie. |
| Ontario | O&S | Rogers 169 | 4/1849 | 4-4-0 | |
| Ontario | P&R | Baldwin | 1844 | 0-6-0 | |
| Ontario | UE 2 | Baldwin 5984 | 1/1882 | 2-8-0 | S 1885 to U&N #280. |
| Onward | BH&E 10 | Schen 526 | 12/1868 | 4-4-0 | Built as Duchess & Columbia RR #100; xf 1873 to NY & New England 10. |
| Onward | E&KR 3 | Baldwin 6711 | 1883 | 2-6-0 | |
| Onward | E&P 2 | Baldwin 3638 | 8/1874 | 2-6-0 | S 1881 to Bodie & Benton #1. |
| Onward | Hinkley | 1887 | 4-2-2 | Built for the Swinerton Locomotive Driving Wheel Company as a demonstrator to show the company's polygonal driving wheel tire; s to Portland & Rochester Railroad as #13; rb by Manchester Locomotive Works as 4-4-0; scr 1905. | |
| Opdyke | ATSF 13 | Taunton 542 | 9/1871 | 4-4-0 | |
| Opechee | H&C | Baldwin | 1891 | 2-8-0 | 3 ft narrow gauge; sold in 1901 to Quincy & Torch Lake Railroad as #5 for use at the Quincy Mines in Hancock, Michigan; preserved but stored outside near Franklin, Missouri. |
| Opelousas | NOO&GW | Baldwin 512 | 2/1853 | 4-4-0 | Built for pred. Opelousas RR; sank off Key West; recovered 5/1853 and rb by Baldwin; became ML&T #1; rn 1885 #501; off roster by 1/1897. |
| Ophir | V&T 16 | Cooke 885 | 1872 | 2-6-0 | Sold 1881 to Oregon Railway & Navigation Co. |
| Orange | Boyden 1 | 1837 | |||
| Orange | C&PR 3 | Hinkley 206 | 1848 | 4-4-0 | Rn Oxbow; off roster by 1884. |
| Orange | NY&E 4 | W Norris | 1841 | ||
| Orange | NYOW 7 | Rhode 121 | 8/1869 | 4-4-0 | Sold before 1880. |
| Oregon | O&C 1 | Baldwin 2001 | 11/1869 | 4-4-0 | Built for Oregon Central; rn 1891 #1106; scr 4/26/1900 Sacramento. |
| Oregon | CV 19 | Baldwin | 1851 | 4-4-0 | Rebuilt 9/11/1861; renamed 3/1869 Bethel. |
| Oregon Pony | OPRR | Vulcan | 1862 | 0-4-0T | 5 foot gauge; Entered Service 5/10/1862; had reverse flue boiler; may have been first loco on West Coast; restored at Cascade Locks Historical Museum, Oregon. |
| Orient | LIRR | Rogers 501 | 6/1854 | 4-4-0 | |
| Orleans | NA&S | Norris | 1851 | 4-4-0 | Became LNA&C 4, Dart, in 1859. |
| Ormsby | V&T 2 | Union 12 | 1869 | 2-6-0 | Sold 3/1925 in Tahoe. |
| Oronoco | CP 93 | R Norris | 7/1860 | 4-4-0 | Ex-Calif Central #1; to Sacramento Valley #6; to CP 2/29/1869; Rn 1891 #1119; rb 8/1872; became SP #17 9/1872. |
| Oroville | CaN 1 | Norris | 1861 | 4-4-0 | Became Northern California #1; rn 1891 #1102; scr 1892. |
| Orray Taft | P&W | Corliss | 1851 | 4-4-0 | Acquired c. 1853; ex-Advance. |
| Osage | KPDP 13 | Rogers 1410 | 1866 | 4-4-0 | |
| Oscar Wilde | CV&S 17 | NG; Taken by Tyler Tap Ry as partial payment for #5 J. W. Paramore. | |||
| Oscar Wilde | O&T 17 (2nd) | Brooks 345 | 2/1879 | 4-4-0 | Ex-Texas & St Louis #5 J. W. Paramore 1882; G. Kingsbury was the designated engineer. |
| Osceola | S&U | Rogers 116 | 1/1848 | 4-4-0 | |
| Oshkosh | LC&M 7 | Schen 117 | 7/1855 | 4-4-0 | Became M&SP #7 in 1863; off roster by 1898. |
| Ossipee | Hinkley 1096 | ||||
| Ostrich | CP 140 | Schen 515 | 10/1868 | 4-4-0 | Rn 1891 #1145; rb 8/14/1871. |
| Oswegatchie | O&LC 4 (1st) | H & Drury 260 | 4/1850 | 4-4-0 | Sold 1/23/1872 to Rutland & Burlington. |
| Oswego | NYOW 1 | Rhode 101 | 4/1869 | 4-4-0 | Sold 10/27/1887 to NY Loco Works; scrapped 1/1888. |
| Oswego | O&S | Rogers 168 | 4/1849 | 4-4-0 | |
| Otero | ATSF 62 | Baldwin 4351 | 6/1878 | 4-4-0 | |
| Otis Drury | CV 79 | CV St Albans | 1871 | 4-4-0 | Rn 1879 #21 to replace 2nd Erie; rn 1/1/1900 #36; sold to NLN 12/1892. |
| Otoe | KPDP 14 | Baldwin 1540 | 1866 | 4-4-0 | |
| Otsego | NYOW 6 | Rhode 120 | 8/1869 | 4-4-0 | Sold 10/23/1886. |
| Otselic | NYOW 41 | Baldwin 2692 | 2/1872 | 4-4-0 | Rn 11/7/1906 to 3rd #28. |
| Otta Quechee | CV 14 | H & Drury | 1848 | 4-4-0 | Rb 9/8/1858; sold 4/1/1884 to SS&C; sold for scrap 1893. |
| Ottawa | CV | Amoskeag | 1851 | 4-4-0 | Rebuilt 11/17/1856; renamed to Farnham before March 1871. |
| Ottawa (1st) | O&LC 8 (1st) | Taunton 25 | 11/1848 | 4-4-0 | Built for Norfolk County RR as Waterford. |
| Ottawa (2nd) | O&LC 28 (2nd) | Malone | 4-4-0 | May have been #8 rebuilt; Rn 1/1/1891 #328; Scrapped. | |
| Otter Creek | R&B 18 | Hinkley 548 | 10/1854 | 4-4-0 | Originally built as Know Nothing; rb 1871; became Central Vermont #209 1891; scrapped 8/1892. |
| Ouray | D&RG 5 | Baldwin 2568 | 1871 | 2-6-0 | Entered service on 10/13/1871; sold to Little Book Cliff Ry as #1 Susie. |
| Owyhee | CP 16 | Mason 223 | 2/1866 | 4-6-0 | Rn 1891 #1511; scr 1/1893. |
| Oxbow | C&PR 3 | Hinkley 206 | 1848 | 4-4-0 | Ex-Orange. |
| Oxford | NYOW 12 | Rhode 132 | 9/1869 | 4-4-0 | Sold 10/24/1887 to NY Loco Works; scrapped 1/1888. |