Is it possible to find the blueprints for my house? It was built in 1969, in southern California.
Do you know the builder and/or architect? That’s pretty far back, even if you do. Some municipal governments store such docs now, but I doubt they did in 1969, nor that their records go back that far.
Why do you need them? Curiosity, or for a remodeling project?
We might be able to come up with the name of the builder, since that company built a large number of homes in this area, but I think they are out of business.
We don’t actually need the blueprints, but yes we are remodeling and we keep finding, uh, interesting things as we go along. Such as, apparently there was another bedroom downstairs at one time. And it looks like when the wall was taken down on that bedroom, the one that is left downstairs was heavily modified.
Lotsa surprises! 
In my work, I have found various building depts. holding (on microfiche) foundation and framing blueprints for houses built in the 1920’s and 1930’s. So it’s not wholly unlikely that you’ll find something from the late 60’s – depending on the sophistication of the municipality involved, at the time of original construction.
Plansets of those early decades were usually extremely minimal. As in: one page fits all.
You do get increasing detail – like electrical specifications, insulation, etc., as the decades march onward. My family’s house, from 1968, had about five pages of plans and elevations.
But even in the 1960’s, residential buildings were often heavily modified from the relatively simplistic plans presented and recorded, as site issues arose. Structural failure modes in wood were poorly understood, and the contractors often had a lot of ‘poetic license’ from the inspectors to…improvise.
And bear in mind that if your contractor was doing a lot of spec or tract homes in the area, they might submit a very generalized set of plans that covered most variations of the house type they were developing.
Final note: I just pulled a set of 1993 plans, from a very good local architect who I respect quite a bit. Even in that recent, extremely-detailed planset (22pages or so), there were major elements that had been located in positions different than what was noted on the stamped plans; electrical locations, venting, certain shear walls and holddowns…
In other words: don’t rely on ANY planset to be a true or final picture of what and where things are living inside your walls. Not to any highly-invested degree, anyway.
Hmmm… my house was build in 2007, and someone left behind a sheaf of drawing just for roof trusses; not that the roof is terribly complex. As for electrical, it was pretty much “wing it”, based on codes. An outlet every 10 feet or so on the walls… “where do you think you’ll put your bed? OK, we’ll put an outlet about where the nightable sits”. Only specific sites like the washer/dryer location had definite locations for outlets. Nothing was planned to the anal detail of “this breaker number is for the first 2 bedrooms” or even the actual runs from the breaker panel. Plumbing? Again, the basic end points were planned but the actual routing was made up as they installed it. However, this was about the 20th house in the area with this floor plan, so not likely any element was surprising or difficult.
In the days before CAD (say, pre-1990) every plan was hand-drawn so you won’t get voluminous detail of plans. Blue-prints were a cheap way of making large-size reproductions cheaply, but I’ve never heard how well they lasted. I know I saw a lot of industrial plans where I worked that the engineers had simply taped blank paper over an area of an old plan to draw the modifications, then made a copy of the result.