In <answer>1941</answer>, the General Anaya borough was merged to the Central Department, which was then renamed "Mexico City" (thus reviving the name, but not the autonomous municipality). From <answer>1941</answer> to 1970, the Federal District comprised twelve delegaciones and Mexico City. In 1970 Mexico City was split into four different delegaciones: Cuauhtémoc, Miguel Hidalgo, Venustiano Carranza and Benito Juárez, increasing the number of delegaciones to sixteen. Since then, in a de facto manner, the whole Federal District, whose delegaciones had by then almost formed a single urban area, began to be considered a synonym of Mexico City.
When was the General Anaya borough officially merged into Mexico City?
1941