My dad was born in 1917 on the plains of eastern Colorado. When he was 75 he came to "visit" me, I was the youngest of 10, and he never left until he passed at 95. He told me that it was common for poor families with lots of kids to basically sell some of their kids when they got to be around 10 years old to bigger farms or ranches because they couldn't afford to feed or clothe them. He told be that he and his brother would be sent to work on their neighbors farms starting when they were 10 or so, plow fields with horses, hauling water from creeks, all sorts of labor. They were never paid, but the family was given a share of the harvest to get them thru the winter. Rinse and repeat until he was around 18, during the dust bowl years and they moved to California. See "Grapes of Wrath".