[451][448] His early views on slavery were no different from any Virginia planter of the time.[452] From the 1760s his attitudes underwent a slow evolution. The first doubts were prompted by his transition from tobacco to grain crops, which left him with a costly surplus of slaves, causing him to question the system's economic efficiency.[453] His growing disillusionment with the institution was spurred by the principles of the American Revolution and revolutionary friends such as Lafayette and Hamilton.[454] Most historians agree the Revolution was central to the evolution of Washington's attitudes on slavery;[455] "After 1783", Kenneth Morgan writes, "...[Washington] began to express inner tensions about the problem of slavery more frequently, though always in private..."[456]
The many contemporary reports of slave treatment at Mount Vernon are varied and conflicting.[457] Historian Kenneth Morgan (2000) maintains that Washington was frugal on spending for clothes and bedding for his slaves, and only provided them with just enough food, and that he maintained strict control over his slaves, instructing his overseers to keep them working hard from dawn to dusk year-round.[458] However, historian Dorothy Twohig (2001) said: "Food, clothing, and housing seem to have been at least adequate".