Engineers, who were the leaders of the Underground Railroad, helped slaves who were running away by providing them with food, shelter, and sometimes jobs. They hid the slaves from people who were trying to catch them and return them to slavery.
The GDP per Capita, in Nigeria, when adjusted by Purchasing Power Parity is equivalent to 32 percent of the world's average.
The United States is a developed country and has the world's largest national economy, with an estimated 2012 GDP of $15.6 trillion â 19% of global GDP at purchasing-power parity, as of 2011.