For four centuries, Americans have been at once tillers of land and speculators in its future value. Like speculators throughout history, some became wealthy, others made less than they thought they should, and still others lost their shirts.

The American farmers in financial trouble these days are only the most recent in a line that stretches back to colonial times. Those in deepest trouble are generally those that borrowed the most to buy more land when the price of farm crops, and thus the land itself, was high. The reason has been the same through the centuries: When the price of livestock and crops went down and the price of land with them, the mortgage payments did not.

"In the words of the old song, the farmer worked hard, but 'the mortgage worked hardest of all,' " recalls Stanley Lebergott in his book "The Americans: An Economic Record," published a few months ago.

To help pay off those mortgages and secure their hoped-for capital gains, farmers throughout American history have urged adoption of colonial, state or federal government policies that would boost farm prices. Sometimes the solution was a generalized inflation, from which the farmers expected to be protected since their wealth was in the form of a real asset whose value would rise. At other times, a high tariff on a particular crop and, more recently, direct support of commodity prices and export subsidies have been the answer.

Lebergott's book is a trenchant series of wide-ranging essays on the nation's economic past and the forces that shaped it. It singles out farming only in the sense that agriculture dominates the first three of the country's nearly four centuries of history; after all, in the beginning, land was the nation's most abundant asset.

There is a strong sense of deja vu in many of the chapters. Some of the issues of the distant past seem little different from those in this year's congressional debates:

* Protection from "unfair" foreign competition and "dumping" of foreign products.

* Enormous dislocations caused by the advent of some new product or some extraordinarily swift advance of productivity.

* States fearful that other states would snatch away their industry by lowering taxes.

* Transportation companies seeking government regulation to ensure them a "fair" profit.

* The lure of a better life in the United States that boosts immigration, leading to efforts to limit the inflow of people -- at least in part to protect "American" labor and wages.

Through it all, Lebergott, a professor of economics at Wesleyan University, emphasizes the uniqueness of the American experience that has flowed from the drive of entrepreneurs, including the farmers, who were willing to take risks -- and who, whenever possible, applied those same entrepreneurial skills to try to insulate themselves from the vagaries of the marketplace.

He also traces some of the sacrifices that were made. "Much attention has recently been lavished on the role of productivity, human capital, and research and development in economic growth," Lebergott writes. "This irresistibly led to a belief that it was primarily such forces that drove real output up during the first century of independence."

That belief is not correct, he says, carefully marshaling as he does repeatedly thoughout the book facts and the work of other economic historians to buttress his view. Instead of great productivity gains, it was labor, land and tangible reproducible capital -- the structures and equipment of households, farms and businesses and the public works of government -- that were largely responsible for the economic growth.

Lebergott also draws on his own work in the history of U.S. labor force and manpower changes. He was responsible, for example, for constructing otherwise unavailable figures for U.S. unemployment rates during the Great Depression. During the 1940s and 1950s, he worked in Washington for the Labor Department and the Bureau of the Budget.

Lebergott recognizes the sterility of the language of economic analysis and tries to restate it in human terms. "The spare simplicity of a 'labor input' series summarizes the market's valuation of the sacrifices in energy and effort made by the pioneer farmers, indentured servants, and slaves," he writes. "A 'capital input' series similarly measures (in financial terms) the extent to which they denied their families such tiny luxuries as sugar and coffee, such conveniences as cabins chinked well enough so that snow did not blow in through the logs.

"Such sacrifices were made because farmers used their time and energy to clear the land of trees and stumps, to repair farm tools, and used their savings to buy still other capital inputs. Indeed, families saved perhaps 12 percent of their incomes in order to make such investments, thus reducing their consumption at more than twice the rate their wealthier descendants did in the 20th century. These were the basic elements in economic growth. . . .

"But once such central 'economic' contributions to growth are recognized we must turn to the contribution made by the values of the people themselves," he continues. "These values drove the 'productivity' gains, for they prompted the American willingness to accept persistent novelty in production. Without such willingness Americans would never have put up with the costs of growth -- job turnover, migration, high depreciation of machinery, destruction of business investments, and the harsh obsolescence of human skills and training."

The most remarkable advances sketched by Lebergott, at least up until this century, came in agriculture: "From its very beginning the U.S. economy had been agricultural. By the outbreak of the Civil War agriculture still employed more than half the entire labor force," and it was primarily performance of the farms that drove American incomes upward.

Around the world, the pattern of land settlement has been a major factor in the speed of economic development, according to a study cited by Lebergott. Slower developers have typically had very small or "parcelized" land holdings, or else the choice of crops or farming methods was decided communally.

"Neither obstacle was present in the United States," Lebergott says. "Millions of untilled acres were available for sale from the earliest days of the nation. Three-fourths of American families owned their own farms even in late colonial days. Farms ranged from 100 to 150 acres, and almost none held the tiny five-acre parcels of many nations. Farmers could see what crops had done well, could make their own judgment of market prospects. They could vary their crop combinations and production techniques from year to year as they chose. Neither chiefs, landowners, village elders, nor the commune had to agree before a change could be made."

It is almost hard to believe some of the figures Lebergott presents about the upward economic mobility farming represented in the colonial period and in the century following independence. In Europe in the 18th century, two acres or less of arable land were needed to feed one person. If one could grow 21 bushels of corn per acre in the United States, two acres would produce enough corn and hay "to provide his food and whiskey, plus food for his horse" -- with his whiskey, of course, made directly from the corn and his pork indirectly.

This intensive use of the land was one reason why the Indians, whose hunting-based existence took 1,000 to 2,000 times as much land per person, were so inexorably displaced.

But if two acres would feed one person, or 20 acres a family of 10, why were the colonial-era farms 100 acres or more? "The typical American in the century from, say, 1763 to 1861 was a farmer, and, as such, a land speculator," Lebergott says. Naturally, there also were speculators who were not farmers.

During the Revolution, "as in later American wars, a host of Americans saw the price of wheat, pork, and other farm products rising. . . . They, therefore, borrowed money to buy farm land. (The celebrated Captain Shays, who led Shays' Rebellion in western Massachusetts in 1786 , apparently had borrowed for not one but two farms. His expressed goal was to close the courts, thus blocking suits for debt.

"Such speculators had saddled themselves with interest rates geared to the inflationary prices in the war and the immediate postwar boom. But after the war farm prices and therefore land prices collapsed. . . . Major speculators . . . ended up penniless, some in debtor's prison. Lesser investors found the value of their land holdings collapsing while their interest payments continued, being geared to the older price level. (City workers were not equally afflicted; the cost of living fell dramatically, so their real incomes had actually not fallen much.)"

As the lands to the west were opened, however, settlers poured across the mountains. In 1796, Congress set the price of federal land for sale at $2 an acre. In 1804, that was cut to $1.25, and for a time offered easy credit to boot.

"One way to dimension that figure is to compare it with what common farm labor earned at the time for a day's work -- about 80 cents in New England and 50 cents in New York. Hence a week's work would buy enough land for subsistence." In 1830, a farm laborer could accumulate enough capital in two years' work to see him through the first year on his own farm.

The work was hard and farming, as always, was full of the risk of failure. But the opportunity was there. Land prices did go up over time, and a farmer could accumulate enough assets to keep him through his old age and leave a livelihood to his children. Urban workers had few such opportunities.

Moreover, when the periodic farm depressions hit, perhaps inflation or some other events would bail out the farmers -- or so they would hope.

Many histories of the post-Civil War era depict a decades-long period in which farmers were hanging on by the skin of their teeth. Farm prices did fall after that war, and mortgages were a burden. However, Lebergott shows convincingly that farm incomes were rising at least as fast as those of the workers in the nation's new factories. In addition, the value of their land also was generally rising.

"Sympathetic historians and novelists continue to treat the 'farm problem' as one long descent into unrelieved misery," Lebergott writes of the latter part of the 19th century. "If the prospects in farming were indeed as bleak as contemporary protest movements and later historians have described, what could have induced almost 3 million persons to become farmers by 1900, nearly doubling the 1870 count? One answer is implicit in the fact that farmers' income and net worth advanced faster than did those of the nonfarm population from 1896 to the mid-1920s. Indeed, the real value of farms rose spectacularly. . . . "

When the Great Depression struck, the federal government got permanently into the business of supporting farm incomes, in one way or another. Each time a new income guarantee is provided, or if farm commodity prices rise for purely market reasons, farmers quickly capitalize that promised flow of income by raising the price they are willing to pay for land.

The current dilemma facing some sorely pressed farmers is one their predecessors faced. The same thing is true of manufacturers confronting competition from foreign goods, and of other sectors of the American economy.

In some universities, Lebergott's book is being used as a textbook in economic history. It provides a sweeping view of the nation's economic past, and often its present and future, too.

"The complexities induced by high economic performance and ever multiplying public goals made it difficut to say where the American economy was headed," he says in his concluding paragraph. "Those who saw it moving in a world committed to 'the contrivance of havoc' could ask Figaro's question instead: 'Who knows whether the world will last three weeks longer?' More confident Americans, looking back at two centuries of tough American achievement, could quote Yogi Berra: 'It ain't over till it's over.' "