Sonora Smart Dodd was raised along with her five siblings by their widowed father, William Jackson Smart, a Civil War Veteran, in Spokane, Washington. Wikipedia reports:
She was inspired by Anna Jarvis's efforts to establish Mother's Day. Although she initially suggested June 5, the anniversary of her father's death, she did not provide the organizers with enough time to make arrangements, and the celebration was deferred to the third Sunday of June. The first June Father's Day was celebrated on June 19, 1910, in Spokane, WA.These plaques, mounted on a rock in downtown Spokane's Riverfront Park, commemorate Mrs. Dodd and her accomplishment in setting aside an official day to honor all fathers. You can read more in this article on the city's website.
Unofficial support from such figures as William Jennings Bryan was immediate and widespread. President Woodrow Wilson was personally feted by his family in 1916. President Calvin Coolidge recommended it as a national holiday in 1924. In 1966, President Lyndon Johnson made Father's Day a holiday to be celebrated on the third Sunday of June. The holiday was not officially recognized until 1972, during the presidency of Richard Nixon.