Extract names of all previous US presidents in the paragraph below:

Context: Muskets with interchangeable locks caught the attention of Thomas Jefferson through the efforts of Honoré Blanc when Jefferson was Ambassador to France in 1785. Jefferson tried to persuade Blanc to move to America, but was not successful, so he wrote to the American Secretary of War with the idea, and when he returned to the USA he worked to fund its development. President George Washington approved of the idea, and by 1798 a contract was issued to Eli Whitney for 12,000 muskets built under the new system.

Answer: The following are names of US presidents in the paragraph above: Thomas Jefferson (or Jefferson), George Washington.