Complex sentence: In 1966, the word "District" was dropped from the official names of the Courts of Appeal, so that each one is officially described as the "Court of Appeal of the State of California" for a particular appellate district.
Split into simpler sentences: In 1966, the word "District" was dropped from the official names of the Courts of Appeal. Since then, each of them is officially known as the "Court of Appeal of the State of California" for a particular appellate district.