There were diverse kinds of documentary photography in the 19th century just as there are today.
Human endeavor
Engineering feats:
Great buildings (Crystal Palace, Paris Opera)
Monuments (Statue of Bavaria, Eiffel Tower, Statue of Liberty)
Railways
Bridges
Shipping (Great Eastern, Suez canal) Les travaux publics de la France (Paris, J. Rothschild, 1878-1882) [Different volumes use photographs to document the public works within France including ports, railways and bridges.]
Medical advances: Discovery of ether (Photographs by Southworth & Hawes)
The effects of progress: Destruction of the mounds (Photographs by Thomas Easterly)
Events: Blondin crossing Niagara Falls (Photograph by J. McPherson)
Family of man
Ethnic surveys: Native Americans (Photographs by W.H. Jackson, Alexander Gardner and later Edward Sheriff Curtis)
Occupationals: Moscow (Photographs by William Carrick), London (John Thomson)
Social conditions: Edinburgh (Photographs by Archibald Burns), Glasgow (Photographs by Thomas Annan), Paris (Photographs by Charles Marville), New York (Photographs by Jacob Riis)
Natural catastrophes
Fire: 1853 Oswego Mills, NY (Photographs by George N. Barnard)
Flood: 1864 Sheffield (Photographs by James Mudd), 1884 Cincinnati (Photographs by B.D. Jackson), 1889 Johnstown (Photographs by George Barker, R.K. Bonine, Langill & Darling)
Earthquake: 1868 California (Photographs by William Shew, Carleton E. Watkins), 1891 Japan (Photographs by Ogawa Kazumasa)
Tornados: 1890 Louisville, KY (Photographed by W. Stuber & Bro.)
Famine: 1878 (ca) Indian Famine (Photographed by Colonel Willoughby Wallace Hooper)
Human tragedies
Grand scale (War, revolts, civil conflict): 1846-1848 Mexican-American War (Photographs by an unknown Daguerreotypist), 1848 Chartist Meeting in London (Photographed by William Edward Kilburn), 1848 Paris Uprising (Photographs by M. Thibault), 1855 Crimean War (Roger Fenton), 1860s American Civil War (Photographs by Alexander Gardner, George N. Barnard, the Mathew Brady Studio and numerous others), 1871 Paris Commune and the destruction of the Vendome Column
Small scale: Murder, assassination, capital punishment, accidental
