On 19 April 1775, British forces were returning to Boston from the battles of Lexington and Concord when they were spotted by Samuel Whittemore.

1775年四月十九日，英军经过列克里敦、康科德两场战役，返回波士顿，途中被撒母耳。惠特莫尔看见了。

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In 1775, the American Revolutionary War began with the battles of Lexington and Concord.

CNN: Friday,

The Waco siege and the Oklahoma City bombing fell on April 19, the actual anniversary of the Battles of Lexington and Concord.

CNN: Boston Marathon bombing: The latest Patriots Day tragedy

Every third Monday of April, America's oldest and most prestigious marathon coincides with Patriots Day, which marks the anniversary of the battles of Lexington and Concord and signals the arrival of spring.

WSJ: Review & Outlook: Terror in Boston