What does the prase 'twenty one snakes' mean?

Ill give 50 points and brainiest if i can. would be grateful for any on this. the industrial revolution moved the united states into a new economic era. using the resources provided respond to the following prompts as they deal with economic development in the united states. using the maps available on the web links tab, explain the economic development of the united states, especially in regard to its emergence as a major industrial power. (focus on industrial sections; cities and towns; territorial growth; agricultural, mineral, and resource regions; coal fields; slavery; value and production; and distribution of agriculture and manufacturing areas.) using the available maps, explain the economic advantages of the physical geography of the united states. explain the gains that the united states made from trade.