Who has the power to create congressional districts and which has resulted in gerrymandering?

The ruling political party, the one who draws the map - Gerrymandering  is the process of gaining political advantage by manipulating district boundaries. In a single-winner electoral system , the ruling party most often resorts to gerrymandering as a way to win more votes in its favor. It is most common in  countries where the elected politicians are responsible for demarcating boundaries.