- O Assassínio de Lincoln
- O Brasil como Império Independente.
- O Desbravador
- O Guardião Do Segundo
- O Homem Mais Vigiado Do Mundo
- O Padre, O Filósofo E O Profeta
- O paraíso destruído: brevíssima relação da destruição das Índias Ocidentais
- O processo de construção da questão quilombola
- O. B. Padgett: A Florida Son
- Oak Island Mystery: Solved
- Oak Island Obsession
- Oak Island Theories: Knights Templar
- Oak Island Theories: Pirates
- Oaths: Mandatory or Voluntary?
- Obama Will Win, But Romney Will Be President
- Object Lessons
- Obra de Francisco Leal Buitrago: Tomo III
- Obra histórica
- Obras de Baltasar Hidalgo de Cisneros
- Obras de Domingo Faustino Sarmiento
- Obras de Juan María Gutiérrez
- Obras de Manuel González Prada
- Obras de Vicente López y Planes
- Odd and Unusual Tales from the Old West
- Odd Girls and Twilight Lovers
- Oduduwa's Chain
- Of This Earth
- Of Water & Wine
- Official Proclamation of Real Moorish American Nationality
- Oh, Oh, Canada!
- Ohio Constitution of 1802
- Oil and American Identity
- Oil and Nation
- Ojibwe in Minnesota
- Oklahoma Almanac of Facts & Humor: Part 1 - Achille to Nowata
- Oklahoma Almanac of Facts & Humor: Part 2 - Okarche to Zafra
- Old Bill Miner
- Old Canaan in a New World
- Old Landmarks and Historic Personages of Boston
- Old Lives
- Old Man Savarin Stories
- Old Ontario
- Old Quebec
- Old West History for Kids - Settlement of the American West (Wild West) US Western History 6th Gra...
- Old-Fashioned Salads
- Old-Fashioned Salads
- Ole Gimlet Eye
- Oliver Wendell Holmes Jr.
- Omaha Dwellings, Furniture and Implements
- Omoo
- On Canada's Frontier
- On Canadian Wings
- On Common Ground
- On Her Majesty's Service
- On Liberty
- On Soldiers and Civilians - Short Stories of the American Civil War
- On the Battlefield of Memory
- On the Duty of Civil Disobedience
- On the Edge
- On the Edge of History
- On the Front Line of Life
- On the Frontier
- On the Goose
- On the Land
- On the Line
- On the Motion of the Heart and Blood in Animals
- On the Wings of Time
- On Their Own Terms
- On This Day
- Once Upon A Picket
- Once We Lived
- Once We Were Slaves
- One Hundred Virgins
- One Hundred Years of Fire Insurance - Being a History of the Aetna Insurance Company Hartford, Conne...
- One Hundred Years of Service Through Community
- One Hundred Years of Struggle
- One Kind of Officer
- One Man
- One Mississippi, Two Mississippi
- One More River to Cross
- One of the Missing
- One Out of Three
- One Soldier's Story: 1939-1945
- Oneida Utopia
- Ontario 1610-1985
- Ontario and Quebec’s Irish Pioneers
- Ontario Book of Days
- Ontario Garlic
- Ontario's African-Canadian Heritage
- Opening Act, The
- Opera Viva
- Operación América Fidel Castro gestor del terrorismo comunista contra Latinoamérica
- Operación Pedro Pan
- Operation Friction 1990-1991
- Opportunity Road
- Orangeville
- Order 14133
- Oregon and the Collapse of Illahee
- Organizing at the Margins
- Original Highways
- Orjien vapauttaminen Pohjois-Amerikassa
- Oro y espadas
- Orígenes hispanos de California
- Os Canadenses
- Os Desafios Da Igreja Anglicana Na Atualidade
- Osgoode Hall
- Oswald is Innocent
- Our Bull's Loose In Town
- Our Dual Citizenship
- Our Frontier Is the World
- Our Italy
- Our Life on Lear's Room, Labrador
- Our Lives, Our Fortunes, Our Sacred Honor
- Our Longest War
- Our New England Ancestors and Their Descendants 1620-1900 - Historical, Genealogical, Biographical
- Our North America
- Our Voices Must Be Heard
- Ours by Every Law of Right and Justice
- Ourselves Unborn
- Out from the Harbour
- Out of Darkness-Light
- Out Of Darkness-Light
- Out of Oakland
- Out of the Blue
- Out of the Shadow
- Out of the Shadows
- Outlaws of the Atlantic
- Outlaws of Western Canada
- Outlines of Zuñi Creation Myths
- Outrage in Ohio
- Outside In
- Over the Rocky Mountains
- Over The Side: Black Marines of WWII