Many Planters did invest in railroads and factories and other "internal improvements". But in the South the trend was toward a greater concentration of wealth in lands and slaves. Per Capita southern wealth rose 62 percent from 1850 to 1860, the average price of slaves rose 70 per cent and the value per acre of land appreciated 72 per cent. While Southern investment in manufacturing (and the means to deliver goods, roads, canals or whatever) only increased 39 percent. In other words Southerners had chosen to invest a larger portion of their capital in slaves and land in 1860 than 1850.
Soltow, Men and Wealth.
Cotton was indeed King in the South. Even with what taxes they paid on imports...no,never exports...James Hammond had this to say in the Senate in 1858...Southerners were "unquestionably the most prosperous people on earth, realizing ten to twenty per cent on their capital, with ever prospect of doing as well for a long time to come." What other improvements or changes could pique their interest with King Cotton.
Hammond to William Gilmore Simms, April 22, 1859, quoted in Nevins, Emergence