During the period of industrialization in the United States, which primarily took place from the late 19th century to the early 20th century, the region that received the most immigrants was the Northeast, with particular emphasis on areas such as New York City and other industrial cities in the region. However, without the details of what Regions 1 through 4 specifically represent, it's challenging to provide a definitive answer based on your response options.
If you can clarify what each region corresponds to, I would be able to offer a more accurate response.