House

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)
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)
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)
Oulagisket (Putnam County, New York)
Outlands in the Eighty Acres (Monterey County, California)
Outlet Gates and Gatekeeper's Cabin (Placer County, California)
Overbrook (Davidson County, Tennessee)
Overcarsh House (Mecklenburg County, North Carolina)
Overfelt-Campbell-Johnston House (Jackson County, Missouri)
Overholser Mansion (Oklahoma County, Oklahoma)
Overholt House (Wayne County, Ohio)
Overlook (Berkeley County, West Virginia)
Overlook (Buncombe County, North Carolina)
Oversen, Julius and Anine House (Woodbury County, Iowa)
Overstreet House (Le Flore County, Oklahoma)
Oviatt House (Winnebago County, Wisconsin)
Stone mansion now serving the University of Wisconsin - Oshkosh
Ovide Broussard House (Vermilion Parish, Louisiana)
OW Ranch (Big Horn County, Montana)
Owen and Margaret Oliver House (Waukesha County, Wisconsin)
A rural Italinate farmhouse that has changed little over its lifetime.
Owen Coachman House (Cape May County, New Jersey)
Owen E. LeFevre House (Denver County, Colorado)
Owen Estate (Arapahoe County, Colorado)
Owen Lovejoy Homestead (Bureau County, Illinois)
Owen Martin House (Stone County, Arkansas)
Owen Plantation House (Jefferson County, Alabama)
Owen Tudor Hedges House (Berkeley County, West Virginia)
Owen--Cox House (Williamson County, Tennessee)
Owen--Primm House (Williamson County, Tennessee)
Owen-Harrison House (Rowan County, North Carolina)
Owens--McCoy House (Jackson County, Missouri)
Owens-Thomas House (Chatham County, Georgia)
Owings House (Pulaski County, Arkansas)
Oxford Historic District (Scott County, Kentucky)
Oxford House (Grand Forks County, North Dakota)
Oxland (Rapides Parish, Louisiana)
Oxmoor (Jefferson County, Kentucky)
Oxon Cove Park (Prince George's County, Maryland)
Oxon Hill Manor (Prince George's County, Maryland)
Ozias Goodwin House (Suffolk County, Massachusetts)
Ozmer House (Columbia County, Arkansas)
P. A. Fry House (Bastrop County, Texas)
P. C. Warner First House (Pinal County, Arizona)
P. J. Heilman House (Logan County, Oklahoma)
P. M. Craigmiles House (Bradley County, Tennessee)
P. P. Raymond House (Poweshiek County, Iowa)
P. W. Inskeep House (Hardy County, West Virginia)
P.D. Gwaltney Jr., House (Isle of Wight County, Virginia)
P.D. Houston Jr. House (Davidson County, Tennessee)
Pablo Soto House (Cochise County, Arizona)
Pace House (Jeff Davis County, Georgia)