From congress.gov - Public Law 98-240, 98th Congress:

Joint Resolution, Designating March 21, 1984, as "National Single Parent Day".

“Whereas in the past, single parent families have not always been an accepted part of society;

“Whereas single parents have struggled courageously to raise their children to a healthy maturity, with the full sense of being loved and accepted is persons, and with the same prospects for adulthood as children who mature with their two parents together; and

“Whereas it is time to recognize the courage and dedication of these parents who work to maintain strong family units and to be responsible members of American society: Now, therefore, be it Resolved by the Senate and House of Representatives of the United States of America in Congress assembled, That March 21, 1984, is designated ‘National Single Parent Day’.”