Jefferson didn't "make" land. He bought the Louisiana Purchase from France.
Thomas Jefferson
It was when the French sold Land to President Jefferson
President Jefferson had sent them out to explore the land.
president Jefferson send Lewis and Clark on an expedition to the west because president Jefferson wanted to learn as much as he can he could about the land (Louisiana) he bought.
a slave breeding farm
Washington and Jackson did a lot of land speculation. Maybe Jefferson and others as well.
the Constitution never said that the president has authority to make land purchases
The land you seek was the Louisiana Purchase
Napoleon. He needed the money to fund his war shenanigans so he sold all his uncolonized land in North America to Thomas Jefferson.
Polk
During Thomas Jefferson's presidency, the United States saw significant territorial expansion. The Louisiana Purchase of 1803 doubled the size of the country, acquiring land from France. Additionally, Jefferson authorized the Lewis and Clark expedition to explore and map the newly acquired territory, which furthered knowledge and development of the western frontier. This expansion provided new opportunities for settlement, trade, and economic growth.