William (Mac) Pinckney, 118, a former slave and sharecropper said to be the oldest man in Prince George's County, died of arteriosclerosis Thursday at Southern Maryland Hospital Center. He lived in Washington.

In a 1979 Washington Post story marking his 116th birthday, Mr. Pinkney shared his secret for long life: "As long as I walk upright and keep His command, He will lengthen my days."

At his birthday party, Mr. Pinckney likened his early days in slavery to "a horror story." "They used to beat my mother when she wouldn't do what they told her . . . and I better not have gotten mad when it happened."

He remembered slavery as a life of "harsh treatment, long hours and hard work in the tobacco, corn and wheat fields that often included indignities such as putting our food -- usually milk and flour -- on the floor and making us eat it."

Later, he recalled, there was the Ku Klux Klan. They "came and took our women and did with them what they wanted," he said, "and you couldn't do nothing about it."

Mr. Pinckney, who suffered from leukemia and a kidney ailment, went on to say he did not resent the mistreatment he had received as a slave, explaining , "If you don't know why I'm not bitter, read the Bible."

His youngest daughter, Elizabeth Johnson, with whom he came to Washington to live in 1968, compared having a centenarian for a father to living with a walking history book.

"We had gotten a firsthand account of what 'Roots' was about before it was written," she said.

Another daughter, Edna McKinney, also of Washington, said the children used to ask him to stop telling stories of his and his mother's lives as slaves because "it began making some of us bitter."

Mr. Pinckney was born into slavery shortly before Emancipation in Croom, in southern Prince George's County, where he lived for more than 90 years. His birthdate has been traced back to 1863, according to relatives.

A sharecropper for most of his life, he helped build the first log cabin church in Croom, in which he later was married. His wife, Bertha Lee, died in 1955.

He was a member of Free Will New Hope Baptist Church in Washington and an honorary member of St. Mary's AME Church in Croom.

Mr. Pinckney was the father of 18 children, of whom eight survive.

Besides Mrs. Johnson and Mrs. McKinney, he is survived by six other daughters, Cora Windsor, Mary Savoy and Essie Carroll, all of Upper Marlboro, Lelia Stevenson of Landover, Gladys Perkins of Suitland, and Annie Taylor of Oxon Hill; 82 grandchildren, 139 great-grandchildren and 43 great-great-grandchildren.