When George Washington announced he would not seek reelection in 1796, the nation was more divided than it had ever been. The battle for power between Republicans and Federalists was the primary political reality of the period. In 1796, the Federalists were winning this battle, and controlled Congress, the judiciary, and the presidency under newly elected John Adams. Adams set out to continue the development of the infant nation and solidify Federalist power and principles of government. His first challenge came in the realm of international relations. In response to the seizure of American ships at sea, Adams began what became known as the Quasi-war, in which neither the US nor France declared war against one another but during which the two sides engaged in naval conflict.
In preparation for a possible open war with France, Adams built up the military through heavy taxes and heavy expenditures. In addition, the Federalist Congress passed the Alien and Sedition Acts. These acts were drafted to protect the United States from foreign threats to national security, but their effect was to imprison or deport immigrants without a fair trial, and to brutally silence all political opposition. Outraged at the gall of the Federalists, the population voted overwhelmingly Republican in the election of 1800, in which Thomas Jefferson emerged victorious.
Jefferson would later describe his election in 1800 as a "revolution" because of the sharp swing in political ideology it signaled in America. Indeed, Jefferson quickly set about tearing down the remnants of Federalist government, beginning with the army and the accumulated national debt. One of the most prominent forums in which he attacked Federalist power was in the judicial system, even going so far as to support the impeachment of two federal judges.
In 1803 Jefferson engineered the Louisiana Purchase, more than doubling the size of the US. The Louisiana Purchase may have been the most important event in the first half-century of American history, immediately opening the West to exploration and settlement. Lewis and Clark, now legends of American history, were the most well known explorers of the Louisiana Territory.
However, the Louisiana Purchase also opened the United States to foreign conflict, as many nations strove to achieve dominance in the affairs of North America. Shortly after the US took possession of the new territory, disputes arose with Spain over its borders. In an effort to solve America's territorial problems, Thomas Jefferson entered into negotiations with Napoleon Bonaparte of France, who saw in the dispute a chance to strengthen France's influence in North America and manipulate international affairs favorably.
Jefferson's willingness to engage in international politics with the conniving Bonaparte spurred some Republicans to leave the party and form a faction known as the Tertium Quids, which while they did not seriously challenge Jefferson's power or that of the Republican majority, showed that disunity was a possibility within the Republican Party and had to be guarded against. Another challenge to Jefferson and to the nation was the Aaron Burr conspiracy, an ill-fated attempt by the former vice president to attack Texas and secede from the Union with settlers from the southwest frontier. These two internal challenges well in hand, Jefferson was able to turn his attention to increasing tensions between the US and both Britain and France.
Britain and France, at war with one another, each tried to use the United States as a pawn with which to harm the other. The United States found itself the victim of an economic war, its merchant ships seized by both nations and its neutrality in jeopardy. Jefferson responded in 1807 with the Embargo Act which isolated the US from the world economically. Though he hoped to force France, and especially Britain, into respecting US neutrality, the US was the first nation to give in, lifting the Embargo Act in 1809 with nothing more than a depressed economy to show for it. Though Jefferson's final endeavor as president was a distinct failure, he is generally considered a success, and the Republicans continued to enjoy the support of the majority of the American people after he left office.