The most prolific serial killer in California state history is the Original Night Stalker, who was active in southern California from 1979-86. He stopped mysteriously in the early 80s, save for an outlier murder in 1986 and a taunting phone call in the early 90s. Later, through DNA testing, he was found to be the same person as the East Area Rapist, a serial rapist that terrorized parts of Sacramento and the Bay Area starting in about 1977. An incredibly detailed rundown of his crime spree is available here.

Among several pieces of evidence, including a poem, a strange essay, and several prank/taunting phone calls, was the hand-drawn map above. It looks like the type of neighborhood that would have been suitable for one of his attacks -- however no one has been able to identify it. It could be a neighborhood in California, however - as his crimes have occurred in odd patterns, it has been suggested that he may have moved back and forth in and out of state. While likely in the continental USA, it could literally be anywhere (eg the midwest, mid-atlantic and Florida have been among states some people suspect).

Heres where you come in...If we can locate this neighborhood, it might provide a huge clue in solving the mystery. Worth a try at least... thanks in advance

EDIT: worth noting that the globular shape in the middle of the neighborhood is a lake (as faintly marked by the illustrator). The cul de sacs appear to have islands in them, and there is some sort of highway clover-style exit ramp in the upper left. Again, keep in mind that this was drawn in the late 1970s.