Marcus J. Bles, 81, a Missouri farmer who came to Northern Virginia in 1939 with $50 in his pocket and six years of schooling and made more than $50 million trading in land, died of pneumonia Jan. 9 at Georgetown University Hospital.

In the 1950s, Mr. Bles assembled the land for the Tysons Corner shopping center, where the Capital Beltway meets Routes 7 and 123. In the 1960s, he sold it for a profit of $19 million. He took a portion of his profits and reinvested it in land several miles to the west along Rte. 7 in Fairfax and Loudoun Counties, then sold off a portion of those holdings for $40 million two decades later.

A self-styled "good ole boy" who liked hound dogs, Stetson hats and string ties, Mr. Bles raised cattle on his holdings and drove a tractor.

He was one of a small group of men who were farsighted enough to see there were fortunes to be made dealing in land during the unprecedented population increases in Northern Virginia that occurred during and after World War II. More importantly, he was one of a much smaller group who were daring, patient, shrewd and lucky enough to make a fortune and hold on to it.

At one point in the late 1960s he owned more than 6,500 acres between Washington and Leesburg, putting him well up among the largest landowners in the area.

The eldest of eight children, Mr. Bles was born on a farm near Kelso, Mo. He attended a one-room school for two or three months of the year while working on a farm the rest of the time. When he was a child he lost his right eye to an arrow while playing cowboys and Indians. He quit school while in the sixth grade, worked on a neighbor's farm for $30 a month for a time, and then went to St. Louis and learned carpentry.

He was in his mid-thirties when he pulled up stakes in Missouri, piled his family in a Model-T Ford and drove to the outskirts of Washington with $50 in his pocket. World War II was on the horizon, and the nation's capital was at the brink of a building boom.

Mr. Bles found work at such construction sites as the Pentagon, National Airport, Bolling Air Field and Fort Belvoir. In 1944, he formed the M.J. Bles Construction Co. By the 1950s this had become one of the largest in Northern Virginia.

But he never lost the land hunger he had acquired as a farm boy, and in 1949 he bought the first parcel that would eventually become Tysons Corner: 72 acres that cost him $55,000, considered top dollar at the time. In all, Mr. Bles acquired 322 acres that he would sell for the Tysons Corner development, and he paid $1.5 million for them.

"Paying them kind of prices around Tysons Corner, everybody said I was crazy," Mr. Bles said, recalling his acquisitions 25 years later.

But he got all his money back by quarrying for gravel. He also raised cattle on the hills overlooking Washington before he sold the property for the shopping center and moved his investments west along Rte. 7, just ahead of the area's surging population.

There, in an area east of Leesburg and west of Rte. 28, Mr. Bles once again found himself holding some of the most valuable undeveloped land in Northern Virginia. He continued to raise his favorite breed of cattle, Santa Gertrudis, and he acquired patents for a variety of farm-related and outdoor equipment: a tree stump-removing machine, a snow basket for attachment to front-end loaders, a wood-splitting machine and a hydraulic pump.

For years he was overseer of a company that manufactured and sold the tree stump-removing machine, a device that had been "designed to take out the biggest stump in Virginia in eight minutes."

He also was glad to be away from Tysons Corner. "Too much congestion," he said.

In 1969 he gave 2,000 acres in Loudoun and western Fairfax counties to Georgetown University Medical Center, where his mentally retarded and epileptic daughter, Marcey Ann, had been treated. She died in 1980. Georgetown, in turn, named a part of its medical school the Marcus J. Bles wing in 1971, and it awarded him an honorary doctor of science degree.

Over the last two years, Mr. Bles sold an additional 2,400 acres, most of it zoned for industrial use, but he retained the rights to his house atop a hill in Ashburn, overlooking Rte. 7 to the south and the Potomac River to the north.

Survivors include his wife, Jill, of Ashburn; a son, Jim, of Leesburg; four sisters, Elizabeth Seyer of Randolph, Neb., Thelma Schlosser and Stella Doghorne, both of St. Louis, and Margaret Gadell of Vienna; a brother, Theodore, of Falls Church; four grandchildren, and five great-grandchildren.