5. About the same time of the organization of Indiana Territory the MISSISSIPPI TERRITORY was organized. More important still was the purchase of the vast region called Louisiana. In 1800 Napoleon had compelled Spain to make a cession of this territory to France. He now authorized his minister to dispose of Louisiana by sale. The President appointed Mr. Livingston and James Monroe to negotiate the purchase. On the 30th of April, 1803, terms were agreed on; and for the sum of eleven million two hundred and fifty thousand dollars Louisiana was ceded to the United States. It was also agreed that the United States should pay certain debts due from France to American citizens--the sum not to exceed three million seven hundred and fifty thousand dollars. Thus did that vast domain west of the Mississippi pass under the dominion of the United States. 6. Out of the southern portion of the great province the TERRITORY OF ORLEANS was organized with the same limits as the present State of Louisiana; the rest continued to be called the TERRITORY OF LOUISIANA. Very justly did Mr. Livingston say to the French minister as they arose from signing the treaty: "This is the noblest work of our lives." 7. In 1801 John Marshall became Chief-justice of the United States. In the colonial times, the English constitution and common law had prevailed in America. When the new Republic was organized, it became necessary to modify the principles of law and to adapt them to the altered form of government. This great work was accomplished by Chief-justice Marshall. [Sidenote: =War with Tripoli.=] 8. The Mediterranean pirates still annoyed American merchantmen. The emperors of Morocco, Algiers, and Tripoli became especially troublesome. In 1803 Commodore Preble was sent to the Mediterranean to protect American commerce and punish the pirates. The frigate _Philadelphia_, under Captain Bainbridge, sailed directly to Tripoli. When nearing his destination, Bainbridge gave chase to a pirate which fled for safety to the harbor. The _Philadelphia_, in close pursuit, ran upon a reef of rocks near the shore, and was captured by the Tripolitans. The officers were treated with some respect, but the crew were enslaved. 9. In the following February Captain Decatur sailed to Tripoli in a Moorish ship, called the _Intrepid_. At nightfall Decatur steered into the harbor, slipped alongside of the _Philadelphia_, sprang on deck with his daring band, and killed or drove overboard every Moor on the vessel. In a moment the frigate was fired; Decatur and his crew escaped to the _Intrepid_ without the loss of a man.