Which U.S. president proclaimed the first nationwide Father's Day observance in 1966?

Lyndon B. Johnson proclaimed the first nationwide Father's Day observance in 1966.

Johnson issued Presidential Proclamation 3730 on June 17, 1966. The proclamation called on Americans to honor fathers on the third Sunday of June and encouraged government officials to display the flag in recognition of the occasion.

This proclamation did not yet make Father's Day a permanent federal holiday. That occurred later, after President Richard Nixon signed legislation in 1972. The distinction matters because presidential proclamations and federal holidays are different legal steps.

Johnson's action came decades after local celebrations began and after earlier presidential support for Father's Day. It helped establish the June observance as a nationwide custom, while the 1972 law supplied permanent statutory recognition. Thus Johnson is the answer for the first nationwide proclamation, not for the later law.