Government figures show that the nation's farm population dropped below 5 million last year, the lowest total in more than a century, comprising 2 percent of the nation's residents.

An Agriculture Department historian said the U.S. farm population may be the lowest since James Monroe was president 170 years ago.

The Census Bureau said this week that an estimated 4,986,000 people lived on farms in 1987, 240,000 fewer than in 1986 and the smallest total since records have been kept.

The Census Bureau started issuing a separate count of farm residents in 1920, but Agriculture Department estimates date back further, with an 1880 estimate of 21.9 million Americans on farms.

The current farm population is not the lowest ever, because the 4.9 million total is more than the nation's total population of 3.9 million counted in the 1790 census, the nation's first.

USDA historian Douglas E. Bowers estimated that the last time the nation had fewer than 5 million farmers was about 1820. While exact figures have not been computed, he said some estimates can be derived.

In 1840, for example, the U.S. population was about 17 million. The number of farm people was estimated at 9 million and was reported to comprise 69 percent of the nation's labor force.

Bowers said the U.S. population in 1820 was 9.6 million and the farm population was estimated to comprise 72 percent of the labor force. Thus, he said, the farm population was probably about 5 million then.

The U.S. farm population grew to a peak of 32.5 million in 1916 and stayed near 30 million until World War II, when a steady decline began.

The total number of people living on U.S. farms fell below 30 million in 1942, dropped under 20 million in 1953 and fell below the 10 million mark in 1970.

By region, about half of farm residents -- 2,529,000 -- lived in the Midwest. Next came 1,430,000 farm residents in the South, 725,000 in the West and 302,000 in the Northeast.