The deaths of Adams and Jefferson on July 4, 1826: a demographic and historical analysis

The near simultaneous deaths of John Adams and Thomas Jefferson on July 4, 1826—the 50th anniversary of the Declaration of Independence they both helped create—stands as one of American history’s most poignant coincidences. This paper examines this event within the demographic context of the 56 signers of the Declaration. By 1826, most Signers had already died; Adams (age 90) and Jefferson (age 83) were among the last survivors. We model the overall mortality patterns of the signers with a Gompertz-Makeham model. Monte Carlo simulations are used to estimate the likelihood and timing of any two signers dying on the same date. The simulations show an ~8.1% chance of at least one such event occurring in any given trial. However, the near simultaneous deaths of Adams and Jefferson, the two most prominent signers, on the highly meaningful “Jubilee” date is highly improbable at only 1 in 20 billion chances. Psychological leverage over the timing of death and other factors might somewhat reduce the odds, but the coincidence remains improbable and remarkable.