Wisconsin Democrat Tammy Baldwin made history on Thursday after taking the oath of office in the U.S. Senate and becoming the first openly gay American to serve in that chamber.

"Now we can officially call her Senator Tammy Baldwin," said Chuck Wolfe, president and CEO of the Victory Fund. "LGBT Americans have finally broken through a glass ceiling that held firm for more than two centuries."

Baldwin defeated her Republican challenger Tommy Thompson in a high-spending race in November.

Baldwin was also the first openly gay candidate to win election to the U.S. Congress as a freshman. She has served in the House of Representatives since 1998.

Watch video, uploaded to YouTube by SenateDemocrats, below: