Maude's house
"I used to break into pet shops and liberate the canaries, but I gave it up as an idea before its time."
Maude's house is where Maude shows Harold her various collections; where she makes him tea; where they make love; where Harold throws Maude an 80th birthday party; and where Maude reveals that she's taken a fatal dose of poison.
Her house was a Pullman railroad car, loaned from the Western Railway Museum in Solano County, and parked on no-longer-existent railroad tracks at Oyster Point in South San Francisco. The location of this scene has changed massively since 1971, and is completely obliterated by the sort of soulless office parks that Maude would have despised. One site claims that the location of Maude's home is 75 to 100 feet north of the intersection of Oyster Point Boulevard and Eccles Avenue.
Gordon located an old USGS map of the area as it was transitioning from what it looked like in 1971 to what it looks like today. You can see the railroad spur (now gone) that crosses Butler Road and then runs parallel to it:
I believe that Maude's house was located on this spur, right between the words "BUTLER" and "RD" on this map. Here's what that spot looked like in 1971, and what it looks like today:
Actually, the 2013 photo is taken a couple of hundred feet to the north of the exact site, because at the exact site, an office building completely blocks the view of the San Bruno Mountains.
Maude's car is still in the collection of Western Railway Museum, and can be viewed by taking a tour of the museum's new $2.5 million Car House, for storing their most important assets:
The tour includes viewing the exterior of this car, but doesn't include a tour of the interior. Special thanks to WRM Secretary John Krauskopf, for giving me and Gordon a personal tour of the car's interior. Following filming, the car was returned to its setup as a parlor car:
The car was so heavily redecorated for use as Maude's house that there's not much specific that's recognizable. But the carpeting is visible in the movie, as is this leaded glass partition:
Fun fact: According to John Krauskopf, the car traveled from the museum to the filming location entirely on the existing rail network. But this trip would not be permitted today ... the chassis of the car is no longer compliant with the government's minimum specs for trains that can travel on public rights-of-way. The car can continue to be moved around the museum's private network of rails, however.