March 10

March 10 is the 70th day of the year, and the American record for it runs from 1848 to 2006 — a span of 158 years. The entry that anchors it: The Treaty of Guadalupe Hidalgo is ratified by the United States Senate, 1848.

The antebellum decades brought the date closer to the country’s central argument. In 1848, the Treaty of Guadalupe Hidalgo is ratified by the United States Senate, ending the Mexican–American War.

The early twentieth century brought industry, air travel and war to the date. In 1945, World War II — the U.S. Army Air Force firebombs Tokyo, and the resulting conflagration kills more than 100,000 people, mostly civilians. The same year, World War II — the United States Army Air Forces conducted a firebombing raid on Tokyo that killed at least 90,000 people.

After 1945 the date reflects a country operating at global scale. In 1968, Vietnam War/Laotian Civil War — North Vietnamese and Pathet Lao forces overwhelmed the American, Laotian, Thai, and Hmong defenders of Lima Site 85. A year later, in 1969, in Memphis, Tennessee, James Earl Ray pleads guilty to assassinating Martin Luther King Jr. He later unsuccessfully attempts to recant. A year later, in 1970, Vietnam War — Captain Ernest Medina is charged by the U.S. military with My Lai war crimes. Seven years on, in 1977, Astronomers using NASA's Kuiper Airborne Observatory discovered a faint ring system around Uranus.

The most recent entries fall within living memory. In 2006, NASA's Mars Reconnaissance Orbiter reached and entered orbit around Mars.

The date is also a birthday. Among the Americans born on March 10: Lorenzo Da Ponte (1749), Italian-American priest and poet; Edward Baker Lincoln (1846), American son of Abraham Lincoln; Hector Guimard (1867), French-American architect; Lillian Wald (1867), American nurse, humanitarian, and author, founded the Henry Street Settlement; and Anna Hyatt Huntington (1876), American sculptor.

March 10 is also a date of endings. Among the Americans who died on it: Harriet Tubman (1913), American nurse and activist (born c. 1820); Myer Prinstein (1925), Polish-American jumper; Wilbur Scoville (1942), American pharmacist and chemist; and Zelda Fitzgerald (1948), American author, visual artist, and ballet dancer.

The date carries formal observance as well — Harriet Tubman Day (United States of America) and National Women and Girls HIV/AIDS Awareness Day (United States). The record for March 10 runs 158 years deep across 8 entries. Read in sequence, the date stops being a coincidence and starts being a through-line.