House

Old Town Plantation (Edgecombe County, North Carolina)
Old Trees (Madison County, New York)
Old Turner Place (Henry County, Virginia)
Old Warrick County Jail (Warrick County, Indiana)
Old Wash Place (Anderson County, Kentucky)
Old Watson Homestead House (Monongalia County, West Virginia)
Old Westbury Gardens (Nassau County, New York)
Old Winters Ranch/Winters Mansion (Washoe County, Nevada)
Oldfields (Marion County, Indiana)
Oldfields (Marion County, Indiana)
Oldham, Mary and Frank House (Ellis County, Texas)
Ole and Carris Johnson Ranch (Meade County, South Dakota)
Ole and Elizabeth Finstad Homesite (Bosque County, Texas)
Ole and Polly Oleson Farmhouse (Washington County, Oregon)
Ole Arilsen House (Sanpete County, Utah)
Ole Bohman House (Latah County, Idaho)
Ole Carlson House (Dodge County, Minnesota)
Ole K. Roe House (Dane County, Wisconsin)
Ole Mickelson Cabin (Grays Harbor County, Washington)
Oliphant House (Sabine County, Texas)
Oliphant--Walker House (Travis County, Texas)
Olivas Adobe (Ventura County, California)
Olive Hill (Chesterfield County, Virginia)
Olive Place (Codington County, South Dakota)
Oliver and Gertrude Lundquist House (Burleigh County, North Dakota)
Oliver and Margaret Jeffrey House (Multnomah County, Oregon)
Oliver Beers House (Marion County, Oregon)
Oliver Blood House (Ravalli County, Montana)
Oliver H. Hovda House (Stillwater County, Montana)
Oliver H. Kelley Homestead (Sherburne County, Minnesota)
Oliver House (Clay County, Arkansas)
Oliver House (Kemper County, Mississippi)
Oliver John Harmon House (Carbon County, Utah)
Oliver N. Ainsworth House (Lawrence County, South Dakota)
Oliver O. Howard House (Clark County, Washington)
Two story wood frame house built in 1879
Oliver O. Stokes House (Harding County, South Dakota)
Oliver P. Fannin House (Floyd County, Georgia)
Oliver P. Jones House (Bastrop County, Texas)
Oliver P. Morton House (Wayne County, Indiana)
Oliver Rice House (Fulton County, New York)
Oliver Sturges House (Chatham County, Georgia)
Oliver White Tavern (Tolland County, Connecticut)
Oliver Wiswall House (Columbia County, New York)
Oliver-Leming House (Cape Girardeau County, Missouri)
Ollinger-Cobb House (Santa Rosa County, Florida)
Olmstead Manor (McKean County, Pennsylvania)
Historic mansion converted to a retreat center
Olmstead Place State Park (Kittitas County, Washington)
Olney (Harford County, Maryland)
Olney, Capt. Stephen, House (Providence County, Rhode Island)
Olof Johnson House (Henry County, Illinois)
Olson House (Knox County, Maine)
Oluf Larsen House (Sanpete County, Utah)
Olvida Penas (Monterey County, California)
Olzie Whitehead Williams House (Wilson County, North Carolina)
Omer/Pound House (Jefferson County, Kentucky)
On The Hill (Mecklenburg County, Virginia)
Onderdonk House (Rockland County, New York)
Onderdonk, Horatio Gates, House (Nassau County, New York)
One-hundred-and-one Ranch (Kay County, Oklahoma)
Oneida Community Mansion House (Madison County, New York)
Onon B. and Betsy Dahle House (Dane County, Wisconsin)
Ooten House (Pawnee County, Kansas)
Opp Cottage (Montgomery County, Alabama)
Opposition House (Middlesex County, Massachusetts)
Ora Holland House (Dubuque County, Iowa)
Private Residence closed to the public
Ora Pelton House (Kane County, Illinois)
Orange Grove (Sumter County, South Carolina)
Orange Grove Court (Los Angeles County, California)
Orange Grove Plantation House (Terrebonne Parish, Louisiana)
Orange Lawn (Sonoma County, California)
Orchards, The (Bennington County, Vermont)
Orem's Delight (Talbot County, Maryland)
Oren Law House and Outbuildings (Bear Lake County, Idaho)
Orgone Energy Observatory (Franklin County, Maine)
Orin Clark House (De Kalb County, Indiana)
Orin Jordan House (Los Angeles County, California)
Orin Mallette Cabin (Taos County, New Mexico)
Orin Porter House (Summit County, Ohio)
Orin Savage Cottage (Franklin County, New York)
Orion Clemens House (Carson City, Nevada)
Orlan A. Hayward House (Minnehaha County, South Dakota)
Orland P. Bassett House (Du Page County, Illinois)
Orland Selby House (Lake County, Ohio)
Orlando (Essex County, Massachusetts)
Orlando Brice House (Eau Claire County, Wisconsin)
Stately Georgian Revival residence
Orlando Coolidge House (Jackson County, Oregon)
Orlando Humason House (Wasco County, Oregon)
Orlando W. Warner House (Grand County, Utah)
Orman-Adams House (Pueblo County, Colorado)
Ormond Plantation House (St. Charles Parish, Louisiana)
Ormonde (Madison County, New York)
Ormsby-Kelly House (Palo Alto County, Iowa)
Ormsby-Rosser House (Carson City, Nevada)
Orna Villa (Newton County, Georgia)
Orndoff-Cross House (Berkeley County, West Virginia)
Historic Home near Martinsburg, WV
Orne, Sarah, House (Middlesex County, Massachusetts)
Orrell House (Baldwin County, Alabama)
Orrin B. Hartley House (Hood River County, Oregon)
Orrin W. and Henrietta H. Robertson House (Milwaukee County, Wisconsin)
Lakefront house modeled after Chateau d'Azey-le-Rideau
Orrin W. Burritt House (Cayuga County, New York)
Orrin White House (Washtenaw County, Michigan)
Orrock, Rev. John, House (Norfolk County, Massachusetts)
Orson Ames House (Oswego County, New York)
Orson Everitt House (Wayne County, Michigan)
Orson Grimmett Bungalow (Bear Lake County, Idaho)
Orson Pratt House (Washington County, Utah)
Orson Rogers House (McHenry County, Illinois)
Orth C. Galloway House (Monroe County, Arkansas)
Orth House (Cook County, Illinois)
Ortiz House (Yuma County, Arizona)
Orton Plantation (Brunswick County, North Carolina)
Orton--Malstrom House (Salt Lake County, Utah)
Orville Jackson House (Ada County, Idaho)
Orville P. and Sarah Chubb House (Martin County, Minnesota)
Orville Waring T., House (Union County, New Jersey)
Ory House (East Baton Rouge Parish, Louisiana)
Osborn House (Bristol County, Massachusetts)
Osborn--Bouton--Mead House (Westchester County, New York)
Osborne House (Ontario County, New York)
Osborne Wells House (Newberry County, South Carolina)
Osborne, John, House (Fairfield County, Connecticut)
Osborne, Prince, House (Essex County, Massachusetts)
Osbornedale (New Haven County, Connecticut)
Osburn House (Scott County, Kentucky)
Oscar Anderson House (Anchorage, Alaska)
Oscar B. Jacobson House (Cleveland County, Oklahoma)
Oscar Blomeen House (King County, Washington)
Oscar C. Diehl House (Midland County, Michigan)
Oscar C. Woods House (Scott County, Iowa)
Oscar Carlson House (Morris County, Kansas)
Oscar Chambers House (Sebastian County, Arkansas)
Oscar Crow House (Lincoln County, Arkansas)
Oscar F. Lyons House (Summit County, Utah)
Oscar G. and Mary H. Burch House (Cole County, Missouri)
Oscar Gill House (Anchorage, Alaska)
Oscar H. Chapman House (Ellis County, Texas)
Oscar Lindsay House (Harris County, Texas)
Oscar M. Booth House (Juab County, Utah)
Oscar M. Gottschall House (Montgomery County, Ohio)
Oscar Nichols House (Scott County, Iowa)
Oscar Olson House (Isanti County, Minnesota)
Oscar P. Thomas House (Taylor County, Texas)
Oscar Roeser House (Hall County, Nebraska)
Oscar Taylor House (Stephenson County, Illinois)
Osgood Family House (Oxford County, Maine)
Osgood Gamekeeper's Lodge (Pitkin County, Colorado)
Osgood Hill (Essex County, Massachusetts)
Osgood, Col. John, House (Essex County, Massachusetts)
Osgood, Nathaniel, House (Androscoggin County, Maine)
Osgood, Samuel, House (Essex County, Massachusetts)
Osgood-Kuhnhausen House (Pitkin County, Colorado)
Oskar G. Stonorov House (Chester County, Pennsylvania)
Osmund Osmundson House (Rice County, Minnesota)
Osmyn and Emily Deuel House (Davis County, Utah)
Ossabaw Island (Chatham County, Georgia)
Ossian H. Sweet House (Wayne County, Michigan)
Osterhoudt Stone House (Ulster County, New York)
Osterloh House (Cape Girardeau County, Missouri)
Osterman House (Walla Walla County, Washington)
Oswald J. Nitschke House (Union County, New Jersey)
Oswald West Coastal Retreat (Clatsop County, Oregon)
Otha Walker Homestead (White County, Arkansas)
Other C. Wamsley House (Ravalli County, Montana)
Othniel C. Marsh House (New Haven County, Connecticut)
Othniel Looker House (Hamilton County, Ohio)
Otho Poole House (Multnomah County, Oregon)
Otis Hospital (Mercer County, Ohio)
Otis House (Yavapai County, Arizona)
Otis L. Brown House (Summit County, Utah)
Otis Starkey House (Jefferson County, New York)
Otis, (First) Harrison Gray, House (Suffolk County, Massachusetts)
Otis, (Second) Harrison Gray, House (Suffolk County, Massachusetts)
Otis--Wyman House (Middlesex County, Massachusetts)
Otranto Plantation (Berkeley County, South Carolina)
Ottawa House (Eau Claire County, Wisconsin)
Early "Boomtown" style commercial building
Otterburn (Bedford County, Virginia)
Otto Brinkmann House (Kendall County, Texas)
Otto Carmichael House (Delaware County, Indiana)
Otto F. Eitel House (Jefferson County, Kentucky)
Otto F. Fiebing House (Milwaukee County, Wisconsin)
Historically significant Ernest Flagg designed stone masonry house.
Otto H. Baring House (Harris County, Texas)
Otto House (Harris County, Texas)
Otto Huechling House (Grant County, New Mexico)
Otto J. Hager House (Allamakee County, Iowa)
Otto King House (Henderson County, North Carolina)
Otto Kulage House (St. Louis, Missouri)
Otto L. Uhlig House (Lawrence County, South Dakota)
Otto Meerscheidt House (Bexar County, Texas)
Otto P. Kissel House (Washington County, Wisconsin)
Two and One Half Story Clapboard House
Otto Ripple Agency (St. Louis County, Missouri)
Otto Schell House (Brown County, Minnesota)
Otto W. and Ida L. Nelson House (Multnomah County, Oregon)
Otway Henderson House (McCormick County, South Carolina)
Otwell (Talbot County, Maryland)
Otzenberger House (St. Louis, Missouri)