Feuding founders John Adams and Thomas Jefferson both died on July 4, hours apart

President Thomas Jefferson, left, and his predecessor, President John Adams.

(CNN)For as long as there have been friends, there have been frenemies.

John Adams and Thomas Jefferson are perhaps America's most famous pair of feuding friends. Their storied relationship began in 1775 and ended abruptly on July 4, 1826, when the two ex-presidents died within hours of each other -- on the 50th anniversary of the Declaration of Independence.
Historians believe Adams' last words were, "Thomas Jefferson survives," muttered in his dying breaths before typhoid overcame him. Jefferson had actually passed away several hours earlier, so Adams' proclamation was incorrect.
Whether or not Adams' mention of Jefferson arose out of spite, bitterness, love or camaraderie, historians will never know. But what is clear is that the men held a mix of respect and contempt for each other and maintained an on-again off-again relationship for five decades.
    Many at the time saw their Independence Day deaths as a sign of divine providence. Today, their intertwined July Fourth passings serve as a convenient metaphor for an American legacy of boundless disagreement and unlikely accord.

    First, friends

    Historians, including Gordon S. Wood in his book "Friends Divided: John Adams and Thomas Jefferson," have long focused on the two rivals' volatile relationship.
    Their friendship began in the early days of the nation, despite their vastly different political views. Adams believed in a strong central government whereas Jefferson championed states' rights.
    John Adams served as the second president of the United States.
    Surprisingly, their contrasting views brought them together, thanks to a deep mutual respect and esteem.
    Adams was elected vice president under George Washington while Jefferson was appointed secretary of state. It was here that their kinship began to splinter.
    After Washington chose not to seek a third term, a power vacuum formed. Adams and Jefferson ran against each other, split on issues like their views of the French Revolution.
    Thomas Jefferson is best known as the author of the Declaration of Independence and the third US president.
    Adams squeaked by with three more electoral votes and won the presidency. In an awkward technicality, the 1796 system called for the second-place contender to become vice president.
    Adams asked Jefferson to join him in forming a strong, bipartisan administration. But Jefferson turned him down.

    Then enemies

    In 1800, Jefferson and Adams faced off again. Things got nasty.
    Members of Jefferson's camp said Adams had a "hideous hermaphroditical character," while Adams' supporters called Jefferson "a mean-spirited, low-lived fellow." (Despite the vitriol, there was no mention of nasty women or deplorables.)
    Jefferson won, and Adams was bitter. He left