Location Detective UPDATE
Of course, the opening Magnolia Theater setting is just a simple Google search. The theater was/is in Burbank, shuttered in 1979, and purchased by Barbra Streisand, to be converted into a recording stage - the Evergreen Studios. (I thought that perhaps it was due to the 1976 remake of "A Star is Born," but the side street is called Evergreen - perhaps just a coincidence to match her hit song title.) It is still a recording studio, with a different name.
Novak's apartment's exterior is a combo of backlot sets, one matte shot and some practical Burbank street locations, where the film ends with a nearby shootout. I could see some signage - J.J. Newberry Dept Store and Curries Ice Cream Parlor - but cannot be certain of the exact street addresses. I Googled both defunct businesses with "Burbank," and came up with a few StreetViews, that don't seem to match. Is the old Newberry store now an Urban Outfitters? UPDATE: Yes, it is the same building. Near the corner of Magnolia Blvd, on San Fernando Blvd.
UPDATE: They did mix and match streets for the shootout. The Curries Ice Cream Parlor was at the corner of Magnolia Blvd and North Cordova, about forty blocks from Newberry. The address is clearly visible in the doorway - 3521. The site is now a Chase Bank, but the surrounding buildings are the same, on both Magnolia and Cordova. (I just started Googling that address, and assumed that they might be nearby, or least on the same streets. The shot/reverse shots are not really close, though.) That small office "complex" that MacMurray walks the women through, is now the Permanent Illusion Med Spa, with some signage saying "Joe Roberts - Optical" (on Cordova).
I have had no luck with tracking down MacMurray's apartment's exterior.......but we know it's in Burbank.
Interesting...if you pause the screen on the blueprint the cops are using, for Novak's apartment, you'll see that half of them don't have bathrooms. It's a quick shot, and freeze framing would have been considered science fiction back then......