Final answer:
Kit Carson was co-responsible for the invasion of Northern California in the 19th century.
Step-by-step explanation:
The individual who was co-responsible for the invasion of Northern California in the 19th century was Kit Carson. He was an American frontiersman and explorer who played a significant role in the westward expansion of the United States. Carson was involved in various military actions, including the California Gold Rush and the Mexican-American War, which led to the occupation of California.
Learn more about Kit Carson's role in the invasion of Northern California