I'm no ornithologist...not even a casual birdwatcher, in fact...but my best guess is that it was a red-tailed hawk, though I have no idea whether it was male or female.
I read that some hawks are monogamous and may defend the same nesting territory for years. They mate in the late winter/early spring, and the eggs hatch in about six weeks.
Later in the day, I spotted two small hawks perched on our back fence, which is probably safe to say were maturing babies, as their size seemed to fit the mating/hatching timeline.
While this may seem at first to have nothing to do with owning a mid-century home, it actually does. We have 21 live oak trees in our back yard, which were probably planted around the time the house was built in 1950, so they are extremely large and very tall...just where hawks like to build their nests. Living in a house with a yard that was established over 60 years ago has all sorts of benefits, including the opportunity to see wildlife you might not see in a newer neighborhood.