American herdsmen as an experiment had driven up herds of cattle to sell to the Red River colonists. This was the beginning of trade with St. Paul. Henceforward, what produce Red River people could not sell to the Hudson’s Bay Company, was sent to St. Paul. Then the St. Paul traders paid higher prices than the Hudson’s Bay Company. Twice a year the long lines of Red River ox carts, like Eastern caravans, creaked over the looping prairie trail of Red River southward to St. Paul with buffalo hides and farm products. These carts were famous in their day. They were built entirely of wood, hub, spokes, rim and tire of wheel, pegs even taking the place of nails. Hence, if a cart broke down on the way, it could be mended by recourse to the nearest clump of brushwood. The Sioux were at this time the greatest danger to the cart brigades, and the settlers always traveled together for protection; but the Indians wished to stay on good terms with the Hudson’s Bay Company, and had the settlers carry an H. B. C. flag as a signal of friendship with the fur traders. Within a few years, twelve hundred Red River carts rumbled and creaked their way to St. Paul in June and September. Simpson had issued Hudson’s Bay Company notes of £1, 5 shillings and 1 shilling, to avoid the account system, and these notes were always redeemable at any fur post for Company goods, but in St. Paul, the settlers for the first time began using currency that was coin. Early in the thirties, possibly owing to the dangers from the Sioux, Governor Simpson ordered the building of the stone forts--Upper Fort Garry as a stronghold for the Company, Lower Fort Garry near St. Andrew’s Rapids twenty miles north, as a residence for himself and trading post for the lake Indians. These were the last stone forts built by the fur trader in America. Of Upper Fort Garry there remains to-day only the old gray stone gate, to be seen at the south end of Main Street in Winnipeg. Lower Fort Garry yet stands as Simpson had it built--the last relic of feudalism in America--high massive stone walls with stores and residence in the court yard. Other operations Simpson pushed for the Company. McLean is sent in ’37 to explore the interior of Labrador. John Clarke is dispatched to establish forts down MacKenzie River almost to the Arctic. Bell goes overland, in 1846, to the Yukon. Murray, later of Pembina, builds Fort Yukon, and Campbell between 1840 and 1848 explores both the Pelly and the Yukon, building Fort Selkirk.