The Winchester Mystery House is a mansion located in San Jose, California. It is believed to be haunted by the victims of the Winchester rifle. It has been a tourist attraction since 1923, a year after Sarah Winchester's death.

Very little of the filming took place in the actual mansion. The mansion's design in reality is extremely cramped, making filming very difficult. As such, most of the mansion's interior needed to be recreated on sound stages.

Sarah Winchester had severe, debilitating arthritis and had a series of short risers, only 3 or 4 inches high, in place of stairs as it was very painful for her to raise her foot more than a few inches.

According to records kept by the Mystery House proprietors today, Sarah Winchester constantly built and rebuilt the house throughout her 38 years in residence. The Winchester house has windows and doors in the floor, doors that open into walls or go nowhere, and stairs to nowhere or into the ceiling. Its total area is around 6 acres (24,000 m²).

The promotional image for the film of Helen Mirren sitting in the carriage in mourning clothes mirrors the only known photograph of the reclusive Sarah Winchester on the estate, which is seen on the tour of the mansion in San Jose, California.

Oliver Winchester's first company was Winchester & Company, a men's shirt company he owned with his twin brother, Samuel. In the 1860s, Winchester invested in Volcanic Repeating Arms Company, which produced a revolver designed by Horace Smith & Daniel Wesson. When the company went bankrupt, he bought the company and cleared the debt of $57,000.

Not much is known about how the Winchester house was furnished while Sarah Winchester lived there. She was incredibly private and generally didn't allow photos. Marion Marriott auctioned off what she didn't want herself soon after Sarah's death, and didn't keep any records of what was auctioned off.

The quotes on the stained glass windows shown at the beginning, "Wide unclasp the tables of their thoughts" and "These same thoughts people this little world," are obscure Shakespearean quotes, and not even from the same play. No one knows why Sarah Winchester chose them.

The real life Winchester house has spider webs incorporated into its design, as Sarah believed that spider webs were good luck.

The directors are twins. Dame Mirren likened the experience to having one mind speaking through two mouths.

The real Sarah Winchester did not know a Dr. Eric Price at any point in her life, including when she had moved out to San Jose, California. Price was a fictional story made up specifically for the movie.

Sarah Winchester and her house are given their own chapter discussion in "Ghostland: an American history in haunted places" written by Colin Dickey in 2016. Historically, Sarah Winchester was living in a time that was uncommon and unusual for women to pursue architecture. She was never licensed. Instead, she practiced and experimented on her own house. When one project would prove to not work out or she would lose interest a new project would be started. Even the projects that were completed will have an off-kilter appearance due to space constraints. It is easier to continue building and expanding the size of various parts of the house and within the house than to tear it out to start over.

According to Wendy Cork, the costume designer on the film, Ms Marriott's (Sarah Snook) large, puffy sleeves are actually much slimmer and smaller than the fashion was at the time.

Partly to avoid confusion with Supernatural (2005), featuring main characters Sam and Dean Winchester, the movie is released in some countries in its original title "Winchester: The House That Ghosts Built".

In real life, Sarah Winchester was 4' 10" while Helen Mirren is 5' 4" tall.

The Travel Channel's show Ghost Adventures (2008) aired two paranormal investigations, Ghost Adventures: Winchester Mystery House (2011) and Ghost Adventures: Return to Winchester Mystery House (2016), which depicted evidence of supposed paranormal happenings at the Winchester Mansion.

Winchester did expand to manufacturing other household goods (including roller skates) but not until the 1920s. Despite being a skilled inventor, Sarah Winchester did not invent roller skates, as implied in the film. They had already been mass-produced for decades in the States by 1906.

The nickname of the house is "The Most Haunted House in America".

Among the records Mrs Winchester (Helen Mirren) keeps on deaths caused by her company's firearms are 1899 - Kris Featherloop, 1902 - Mr T Weilloy, 1897 - Sheila Ashton, 1903 - Edward Troft, 1881 - Namrita Singh, 1893 - Frederick North, 1893 - The Norman Brothers.

Dr. Eric Price states he is $300.00 in debt and the company attorney offers him $600.00. Currency Inflation in 2018 equals, in 1916, $6936.00 and $13,872.00, respectively. The 1916 inflation rate was 7.92%. $1 in 1916 is equivalent in purchasing power to $23.12 in 2018, a difference of $22.12 over 102 years (an increase of over 2000%).

Tourists have not been allowed to take photographs as far back as 1989. In 2009, well before Lionsgate bought the film rights, The Asylum film company released a low budget horror film called Haunting of Winchester House and did so without the permission of the Winchester estate as the house is privately owned and operated as a tourist attraction. It was explained that someone connected with the filmmakers surreptitiously took photographs of the interiors of the house on several of the tours in effort to get schematics of enough of the floor plan and of the interiors . The estate has never allowed filming inside the house or grounds for that reason.

Due to the age of the house and the condition of the Victorian interiors, flash photography has never been allowed on the tours.

Despite the title of this supernatural themed movie, Winchester is unrelated to the Supernatural TV series which has the Winchester brothers as its principal characters.

In the movie Sarah Winchester claims that 13 nails are necessary to retain the ghosts in their respective rooms, nailing a wooden piece in the door. It is a nod for the real life Sarah Winchester, who was obsessed with number 13: her house has 13 candles and wall clothes hooks are in multiples of 13; a spider web-patterned stained glass window contains 13 colored stones; and the drain covers on the sinks have 13 holes. In Sarah's tribute, the house's groundskeepers have created a topiary tree shaped like the numeral 13 and every Friday the 13th the large bell on the property is rung 13 times at "1300 hours" (13:00 PT, 1:00 PM) in tribute to her.

The massacre at the Winchester showroom was purely fictional--it never happened.

The 1906 earthquake happened in the early morning, around 5 am, not midnight. The top three storeys of the house collapsed, and multiple rooms were shut up permanently at this time as being unsafe.

In the scene of the 1906 San Francisco Earthquake, someone dies, but in real life the only casualties were couple of cupolas (dome roofing) and a tower.

The room where Sarah is 'channeling' spirits to draw architectural designs is a recreation of a real room in the house known as "the witch's cap." If you look closely, the walls taper in; the real room is conical so the walls come up into a point.

The real Marion Marriott went by the name "Daisy," had no son (though she adopted a daughter after 1906), and left Sarah Winchester's employ as a secretary before 1906 to marry into the Marriott family (no relation to the hotels). Also, her husband did not die tragically.