Washington (CNN) -- There is no constitutional requirement that the Supreme Court preside over the inaugural - it's just been that way and a little history was made around that on Sunday.
Chief Justice John Roberts delivered the oath at the White House to President Barack Obama for a second term.
Just prior, Justice Sonia Sotomayor swore in Joe Biden to another four years as vice president, becoming the first Latina jurist to administer an inaugural oath.
Biden was instrumental in Sotomayor's vetting and ultimate selection by Obama for the high court and said it was an "incredible honor" for him to have her deliver the oath.
The justice told CNN's Soledad O'Brien on Friday that she was not feeling anxious about the inaugural duties, but rather viewing the responsibilities as "surreal."
"I was thinking just a couple of days ago, if I think back when I was a kid which of the two would seem more improbable to me I realized each one was so far fetched that I couldn't have imagine either," she said—sitting on the Supreme Court "and swearing in the vice president in front of the nation and the world."
Sunday's vice presidential inauguration at the Naval Observatory, where Biden lives, was moved up to accommodate Sotomayor's scheduling conflict.
"I want to explain to you what a wonderful honor it was and how much out of her way the justice had to go," Biden said. "She is due in New York. She has to leave right now, so I apologize."
Sotomayor then headed out to catch a train to the Big Apple for a book signing for her new autobiography, "My Beloved World."
The swearing in went off without a hitch, which Sotomayor said was a result of careful planning on her part.
"When you read my book, you realize I practice everything I do over and over again," she told CNN.
Like Roberts, Sotomayor had the oath written on a small card.
After delivering it, she offered a simple "congratulations."
She will be back in Washington for Monday's public swearing in at the Capitol where she will administer the oath to Biden again. Roberts will do the same for Obama.
Obama sworn in during private ceremony
The Constitution requires executive officers, including the president, as well as members of Congress and federal judges, to "be bound by oath or affirmation."
But nothing mandates a Supreme Court justice administer it. When it comes to the presidential inauguration, they just have done so most of the time.
There was no Supreme Court formed when George Washington took the first oath of office in 1789, so New York's highest ranking judge did the honors at Federal Hall on Wall Street.
Four years later, Associate Justice William Cushing swore in Washington for a second term, beginning the Supreme Court tradition.
Early inaugurals were usually conducted in the House or Senate chamber.
The 1817 inaugural was held outdoors for the first time when James Monroe took the oath in front of the Old Brick Capitol, where Congress met temporarily after the original Capitol was burned by British troops in the War of 1812.
The Monroe swearing-in site is now the Supreme Court building.
The man who handled the duties 196 years ago was John Marshall, widely acknowledged as the most influential chief justice in U.S. history. He participated in a record nine swear-ins, from Thomas Jefferson to Andrew Jackson.