Lyndon B. Johnson
Most legislation is signed at the White House.
It was signed into law on July 30, 1965 by Lyndon B. Johnson.
Presumably all presidents have signed laws. You need to specify which law.
When it is signed by the president
Oh, dude, that's easy - it's Medicare! President Johnson signed the Medicare program into law in 1965 as part of his Great Society initiatives. So, like, if you need to thank someone for helping seniors get healthcare coverage, you can totally send a thank you card to LBJ.
On Nov. 2, 1983, President Ronald Reagan signed the King Holiday Bill into law.
President Bush Sr.
President Harry Truman
Medicare was signed into law on July 30, 1965. The program was started to provide health insurance coverage for senior citizens.
President Obama has not signed any law pertaining to same-sex marriage. President Bill Clinton signed the Defense of Marriage Act in 1996. That is the current federal law on this matter.
I think it was President Kennedy.