Which states at the constitutional convention argued against counting enslaved people

Only the Southern states had large numbers of slaves. Counting them as part of the population would greatly increase the South's political power, but it would also mean paying higher taxes. ... They argued in favor of counting slaves. Northern states disagreed.

it was on the rise and doing very well and would continue to do well until the great depression from 1929-1939

the name of the theory is landmass theory.