Final answer:
The greatest increase in the number of immigrants in the early 2000s cannot be determined without a specific map, but general patterns suggest the West may have experienced a significant population increase related to immigration.
Step-by-step explanation:
The question regarding which region of the US experienced the greatest percentage increase in the number of immigrants in the early 2000s cannot be answered definitively without a specific map to reference. However, based on the extracted information about migration and immigration patterns, and general trends in the US, it seems that the West region saw a significant increase in the nation's poor due to these patterns, indicating a likelihood of substantial immigration. In contrast, information about the practice of potlatch, which is associated with the Pacific Northwest, the Mourning Wars with the Northeast, and the role of West Africa in the Trans-Atlantic slave trade, does not directly relate to the question about immigration patterns in the early 2000s, but rather provides context on different cultural and historical aspects.