I think you're mostly right; that's when it got really big. But it began long before...

Standard Oil, United Fruit Company, JP Morgan, DuPont, CitiBank, Associated Press, Pfizer, Macy's, and I haven't even gotten to the Civil War era yet.

   http://en.wikipedia.org/wiki/Corporate_raider
   http://en.wikipedia.org/wiki/List_of_oldest_companies#1825_to_1851
   http://en.wikipedia.org/wiki/Wall_Street#Nineteenth_century