Emerson M. Brooks, 77, a retired official of the Department of Agriculture who wrote a history of the United States and another of the Crop Reporting Service, died of cancer Sept. 7 at Arlington Hospital.

Mr. Brooks, who lived at Rossmoor Leisure World in Silver Spring, was born in Merwin, Mo. He grew up in Ottumwa, Iowa, graduated from Iowa State University with a degree in agricultural economics and later earned a master's degree in history at American University.

He joined USDA's Crop Reporting Service in Iowa in 1934 and was transferred to Washington in 1939. He was engaged in training programs and in the development of data collection and statistical methods for the service. In 1946, he was assigned briefly to the U.S. military government in Berlin. He retired in 1972, after receiving Agriculture's Meritorious and Superior Service awards.

In addition to being the author of numerous technical papers, Mr. Brooks wrote two books, "The Growth of a Nation," which was published by E.P. Dutton and distributed abroad by the State Department, and "As We Recall," a history of the Crop Reporting Service from 1933 to 1961.

He was a member of the International Association of Agricultural Economists, the Inter-American Statistical Association and the American Historical Association. At Rossmoor, he was a member of the Inter-Faith Chapel and the Kiwanis Club.

Survivors include his wife, Helen, of Silver Spring; a son, Marshall, of Vienna; a brother, Harold, of Howey In The Hills, Fla., and two granddaughters.