The reform movements that arose during the antebellum period in America focused on specific issues: temperance, abolishing imprisonment for debt, pacifism, antislavery, abolishing capital punishment, amelioration of prison conditions (with prison's purpose reconceived as rehabilitation rather than punishment), the humane treatment of animals, the humane and just treatment of Native Americans, the establishment of public institutions for the care of the destitute, orphans, blind, and mentally ill, the establishment of public schools, the abolition of tobacco use, vegetarianism, health reform, homeopathic medicine, woman's rights (including, at first, especially the establishment of a woman's right to own property apart from her husband and her right to sue for divorce), and the amelioration of labor conditions (including higher pay, the right to form unions, the right to strike, and the demand for limits on the number of work hours, and safe working conditions).

Although many people became convinced or active in one or two of these issues, the leading activists for these causes were often interchangeable, and would meet at loosely linked conventions of reformers, where they shared enthusiasms and political strategies, and jostled for leadership niches in the various reform movements. All these causes did not arise at the same time, but were added or fully articulated one by one. As each arose, many reformers—who took to calling themselves "universal reformers"—took them on and added them to their own collection of causes.

Reform activists during the early part of this period, from about 1820 to about 1840, believed that they could bring about the needed reforms essentially through convincing people, one by one, of the rightness of the cause, or by preaching at them to cause individual "conversion" to the cause. This was called "moral suasion." Unfortunately for the reformers, this did not always bring the success that they wished for—somehow people would not come around to their beliefs, or, at least, not enough of them to spontaneously change the situation that needed reforming. Many reformers, then, abandoned "moral suasion" as their leading strategy and accepted (often, at first, grudgingly) the need for "associated" effort, meaning in the beginning, efforts to organize associations to advance their causes through political action of various kinds. When even this was not found to bring about the desired reform, advocates of these causes—most particularly, of course, anti-slavery activists—began to accept the rightness of using coercive means by the state, including military and police force, to initiate and enforce the reform.

The reformers were often nourished by Anabaptist roots—especially Baptist or Quaker—or by a form of faith that was essentially a moralizing Puritanism stood on its head, which is to say, Unitarianism, whose forebears were strict Puritans, but who had concluded to reform its doctrine of "endless misery," into an optimistic one of a progressively more joyful heaven on earth. This introduced a utopian, millenialist, perfectionist strand into the reform movement, and was responsible for the innumerable small and large efforts to "come out" of the larger society and set up smaller enclaves or utopian communities, such as the well-known Brook Farm community in Massachusetts. Many of these "come outers" soon "came out," not only of religious sectarianism, but of theistic belief altogether, becoming explicit "Free Thinkers" or atheists. Unsurprisingly, the center of the reform movement was New England (especially Boston) and areas further west, like Ohio and then Michigan, where New Englanders were resettling.

Taken together, many of the reforms coalesced around the larger notion of changing society into a socialist paradise. This is not a later interpretation of what the self-declared reformers were up to, but was often expressed by the leading reformers themselves, who were individually attuned to philosophical and political trends in Europe, especially in France, Germany, and England, as they evolved after the radicalism of the French Revolution, and the resulting efforts there to abolish monarchies and long-established religious authorities. American reformers read this essentially as an effort to endow each person in an egalitarian society with a supreme autonomy over his or her own affairs. They discovered, however, a paradox at the heart of this effort—autonomous people were wayward and often needed to be coerced into egalitarian reform, which meant that a larger authority, such as the State, needed to negate individual autonomy in order to bring about an egalitarian society. Such has been the paradox at the heart of socialism ever since.

Historians have often focused on the antebellum period as the "era of reform" in America, culminating in the anti-slavery crusade of the Civil War, but it is also true that 1865 did not mark the end of the reform movement, but initiated a period that persists until today in which reformers, seemingly vindicated by the end of slavery as a result of the war, shifted their thinking so as to focus on the secular State, particularly the federal government, as the main instrument for reforming society along Progressive lines.

The short answer is this: If you mean full-time work (with certain exceptions) ―none were employed, at least legally.

This was the result of the signing into law in 1938 (two years before) of the Fair Labor Standards Act. Wake Forest University Economics Professor Robert Whaples puts it succinctly: "the Fair Labor Standards Act of 1938 prohibited the full-time employment of those 16 and under (with a few exemptions) and enacted a national minimum wage which made employing most children uneconomical." Whaples describes the various reasons, apart from the enactment of federal, state, and local laws, why the numbers of children working in industry and on the farm had already declined dramatically over the first few decades of the 20th century before the passage of the Act.

The provision of the Fair Labor Standards Act (FLSA) that dealt with child labor stated: "No employer shall employ any oppressive child labor in commerce or in the production of goods for commerce or in any enterprise engaged in commerce or in the production of goods for commerce."

The FLSA, as further defined by statute, prohibited children under 16 from any kind of employment in certain hazardous kinds of work. The Secretary of Labor has periodically revised such categories of hazardous work. For agricultural work, for example, those under 16 should not be employed in operating a tractor of over 20 horsepower, or a hay baler, a forklift, a power post-hold digger, or a chain saw. Nor should they work in a yard or stall in which there is a bull, boar, or stud horse, a sow with suckling pigs, or a cow with newborn calf.

The FLSA also prohibits those under 18 from certain kinds of occupations altogether. These include occupations that require working with explosives or radioactive materials, operating most power-driven woodworking, baking, or meat processing machines, as well as most jobs in mining, meatpacking, logging, and brick-making.

The FLSA exempts certain kinds of work, including employment of children by their parents, and church work. Boys and girls also worked (as they do today) at jobs not covered by FLSA regulations, such as office or clerical work, retail sales positions, food preparation, caring for younger children, and so on.

Given these exemptions, what was the actual number working in 1940?

Gertrude Folks Zimand, General Secretary of the National Child Labor Committee, in "The Changing Picture of Child Labor," published in 1944 in the Journal of the American Academy of Political and Social Science (pages 83-91), reported that the 1940 census showed, among 14- to 15-year-olds, a total of 4,347,665 attending school, and a total of 209,347 gainfully employed (no number was reported for children ages 7-14 who were not in school but were gainfully employed, but the number of these children attending school was 15,034,695; the numbers for 16- to 17-year-olds were 3,361,206 in school and 662,967 gainfully employed). The term "Gainfully employed" included full- and part-time work, either in industry or agriculture. There was some overlap in these numbers because some children were in school but were also working, at least part-time. But according to Zimand, 64 percent of the 14- to 15-year-olds and 83 percent of the 16- to 17-year-olds who were working were out of school and were therefore presumably working full time.