When historians write the history of the U.S. Senate, they'll note that the number 1,907 was a particularly vexing figure for the institution.

So was 672.

And while it wasn't nettlesome, historians will take particular note in the number 1,883

With few exceptions in its 220 years, the Senate has had little trouble determining who is eligible to sit in what sometimes described as the "world's most-exclusive club."

Which brings us to the unique nexus of Senate integers 1,907, 672 and 1,883.

After weeks of wrestling and protestations, Sen. Roland Burris, D-Ill., Thursday became the 1,907th member of the United States Senate. He succeeds the man who just four years ago, became the 1,883rd member of the Senate, President-elect Barack Obama.

Certainly the Senate grappled before with whether to seat certain people. After months of investigation in 1975, it declared a New Hampshire Senate seat vacant after the state sent two competing election certificates for different candidates to Capitol Hill.

But before Burris, it's doubtful the Senate faced such consternation over whether or not to seat someone since 1870. In that instance, the conflict centered on number 672.

Following the Civil War, the Mississippi Senate elected Sen. Hiram Revels, R-Miss., to represent the state in Washington. In those days, state legislatures picked U.S. senators. And Revels would become the first African-American U.S. senator.

The problem was that southern Democrats opposed Revels. They argued he couldn't be seated because blacks didn't become citizens until 1868. And the Senate required nine years of citizenship. Finally, the Senate voted 48 to four to seat Revels.

The problem for Burris is that indicted Illinois Governor Rod Blagojevich, D, tapped him to succeed Mr. Obama in the Senate. The Feds indicted Blagojevich for allegedly trying to auction off the President-elect's Senate seat. And because of that, Senate Majority Leader Harry Reid, D-Nev., called the Burris's appointment "tainted."

But after much tumult, the Senate leadership relented and agreed to seat Burris. Burris's smile gleamed after he was sworn-in and he walked to a lunch in his honor in the Mike Mansfield Room just steps from the Senate floor.

The whole scene pleased Rep. Bobby Rush, D-Ill., an African-American Congressman who went to the mat to have Burris seated.

"Anytime you're reasonable with reasonable people, reason wins," said Rush.

But just last week, Rush sounded anything but reasonable when the Senate Democratic leadership refused to seat Burris

"While they might not be termed racist, their action is racist" Rush said in an exclusive FOX interview.

He also suggested that race led Senate leaders to block Burris.

"I think that if Roland Burris hadn't been an African American, then he would have been allowed to accept the appointment and become a senator," Rush said.

Rush's remarks spurred Harry Reid's spokesman Rodell Mollineau to declare Rush's comments "outrageous and over the line."

But Thursday, Rush argued that his verbiage of a week ago was reasonable.

"It was accurate at that time," he said. "It's a new day."

Rush said that he played a "minor role" helping to get Burris seated. He emphasized that seating Burris made the Senate more diverse as he succeeds Mr. Obama as the only African-American in the body. And the sixth black senator in history.

"It was a long and tortuous path," said Senate Majority Whip Dick Durbin, D-Ill., of the tumult to seat Burris, someone he's known for 30 years.

So now that Burris became the 1,907th person to sit in the Senate, the 1,908th person will be Vice Pres.-elect Biden's successor, Edward Kaufman.

But the numbers game is far from settled in the restless U.S. Senate.

Democrat Al Franken continues to argue he defeated Sen. Norm Coleman, R-Minn.

That dispute is now in the courts after a recount.

"Minnesota, God bless them, has figured out a way to make this more complicated than any other state in the union," said Durbin.

In other words, will Franken could become senator 1,909. Or will Coleman retain his seat as 1,874.

Chad Pergram covers Congress for FOX News. He's won an Edward R. Murrow Award and the Joan Barone Award for his reporting on Capitol Hill.