This costly failure has been ascribed also to the reluctance of white labor to perform any duties to which slaves might be assigned. Slave owners and white laborers held in mutual repugnance the employment of white men at such tasks. According to Olmsted,[8] slave owners have held that the poor whites would refuse to do such work if possible, and, if compelled to submit, would do only so much as they found absolutely necessary. Under all circumstances they do such work reluctantly and "will not bear driving." "They cannot be worked to advantage with the slaves, and it is inconvenient to look after them, if you work them separately."
The natural consequence of the policy thus pursued by Virginia was, despite the fact of her early command over greater wealth and a larger population than the other States, to force her to descend, in part, from her former high estate.[9] A comparison of values of the agricultural lands of Virginia and Pennsylvania, in 1850, shows those of the latter, although of smaller acreage, to have a larger sale value an acre and a larger total value. A similar comparison between Virginia and New Jersey gives the same result.
That the conditions stated as obtaining in 1850 had long existed there seems to be no lack of evidence. Thomas Marshall made, in the Virginia legislature of 1831-'32, searching and detailed statements of the declining wealth and productivity of the State.[10] Such conditions as he pictured made plain that the planters of Virginia must either improve their lands by rehabilitating the soil, acquiring better farming implements, and improving their plow animals,[11] or migrate to the more promising lands elsewhere, or sell their slaves. The records show that by some planters one or another of these methods was adopted. Moreover, Maryland, a sister State of Virginia, because of the exhaustion of her soil by tobacco culture, found essential to her relief the same procedure.[12] With reference to Maryland, the census of 1840 shows an actual decrease over that of 1830 in the slave population[13] of the commonwealth.
To what parts, then, did these slaves go? The theatre of the largest expansion of slavery[14] was the "Western Cotton Belt," the section which shall be herein considered, comprehending parts of Alabama, Mississippi, Louisiana, and Eastern Texas. The chief distinction between the soils of these States constituting the Atlantic Coastal Plain from Virginia to South Carolina and those of the "Western Cotton Belt" is the occurrence of extensive limestone belts in the latter. "The soils in these limestone belts are largely residual, calcareous and usually have a humus content, which gives the soil its black color"[15]—hence the name "Black Belt." The soils of these belts contain much clay and require careful preparation, but they are durable and extremely fertile. Moreover, an excellent water navigation[16] extending well into the region constituted an additional factor in the extension of the cotton culture and of Negro slavery into this territory.
According to Phillips,[17] the lands of the "Western Cotton Belt," most preferred in the early period, lay in two main areas, the soils of both of which were more lasting and fertile than those in the interior of the Atlantic States. "One of these areas formed a crescent across south-central Alabama, with its western horn reaching up the Tombigbee River into northeastern Mississippi." The soil of this area was of black loose loam. Everywhere it was thickly matted with grass and weeds, except where there was visible "limestone on the hill crests and prodigious cane brakes in the valleys." This tract known locally as the prairies or "Black Belt" was smaller than the other which extended along the Mississippi, on both sides, from northern Tennessee and Arkansas to the mouth of the Red River. This tract contained broad alluvial bottoms, as well as occasional hill districts of rich loam, the latter being especially noticeable around Natchez and Vicksburg. The broadest expanse of these bottoms, the Yazoo-Mississippi Delta, received but few migrants prior to the middle "thirties." The planters seem to have settled first in the bottoms, while the other choice lands were competed for by the large and smaller planters, as well as the poor farmers.
These lands were not only, by soil and climate, ideally suited to the production of cotton, but they were reasonably cheap in price. As late as 1849 there was much uncultivated, though fertile agricultural land in each of the cotton-growing States. At that time the total acreage and the area in use in several of the Gulf States were listed as follows:[18]
| State | Total No. of Acres | Acres Owned |
| Alabama | 32,462,080 | 15,911,520 |
| Louisiana | 29,715,840 | 6,263,822 |
| Mississippi | 30,174,080 | 15,811,650 |
There was under these circumstances small wonder that there migrated planters from the worn-out lands of the seaboard slave States, including the less fertile districts of Georgia,[19] and parts of Kentucky and Tennessee. In the absence of statistics giving the exact number of slaves migrating thus with their owners, the estimates of contemporaries and of later writers may be serviceable. The Virginia (Wheeling) Times said[20] that intelligent men of that day estimated the number of slaves exported from Virginia, during the year 1836, to be 120,000, of whom two-thirds (80,000) were carried south by their masters. The Quarterly Anti-Slavery Magazine (vol. ii, 411, July, 1837) gives the Natchez Courier as the authority for the estimate that during 1836 as many as 250,000 slaves, some of whom were accompanied by their masters, were transported from the older slave States to Alabama, Mississippi, Louisiana, and Arkansas.[21] P. A. Morse, of Louisiana, writing in 1857, says that "the augmentation of slaves within the cotton States was caused mostly by the migration of slave owners." On the basis of sources accessible to him, Morse estimated that three-fifths of the slaves removed from the border States to the farther South, from 1820 to 1850, migrated with their masters.[22] Accepting the "three-fifths estimate" of Morse, Collins has made deductions which indicate that approximately 15,900 slaves went south annually with their masters during the decade from 1830 to 1840; while during the next decade the annual migration was about 9,000.[23]
One of these migrant planters,[24] who, in 1835, left his tidewater estate in Gloucester County, Virginia, was Colonel Thomas S. Dabney. Prompted by the necessities of his family to seek more favorable soil, he sought land in Alabama, Louisiana, and Mississippi, finally settling in the one last mentioned. Colonel Dabney carried with him more than two hundred slaves, established himself on a plantation of four thousand acres, and each year contrived, by clearances, to put under cultivation an additional hundred acres. Planters of this type, with large numbers of slaves and sufficient funds to extend their holdings, tended to concentrate both slaves and lands in a few hands.
If the demand for new lands brought great numbers of slaves southward during the years from 1830 to 1850, there were also at work forces which caused many other slaves to be exported in the domestic slave traffic. The extension of the cotton culture in the more southern States, the increased exportation of cotton, the advancing profits therefrom, the development of large sugar plantations in Louisiana, and the decreased average working life of the slave created among the planters of this region an extraordinary demand for slave labor. At the same time such seaboard States as raised tobacco were suffering from a depression in the tobacco markets. The African slave trade, moreover, had been legally suppressed, thus rendering the seaboard and other border slave States the sole legal source of supply for the slave labor required by the lower South.