Associate Justice Antonin Scalia, the longest-serving member of the U.S. Supreme Court, died in his sleep this weekend while visiting a ranch near Marfa, Texas. Scalia was 79.

The cause of death is unknown, though a government official said Scalia told friends he wasn't feeling well before going to bed Friday night.

"Our colleague Justice Antonin Scalia has passed away," Chief Justice John Roberts said in a Supreme Court statement. "He was an extraordinary individual and jurist, admired and treasured by his colleagues. His passing is a great loss to the court and the country he so loyally served. We extend our deepest condolences to his wife Maureen and his family."

Scalia was an outspoken opponent of abortion and same-sex marriage, a proponent of the death penalty and Second Amendment rights, and an overall supporter of "originalism;" the theory that the U.S. Constitution's written interpretation does not change over time.

Scalia was known for brazen opinions on issues he didn't agree with.  

In 2004, Scalia recused himself from Elk Grove Unified School District v. Newdow; a case questioning whether the words "under God" in the pledge of allegiance violate a portion of the First Amendment. Two years later, he drew criticism from retired military officials after saying he wouldn't give a Guantanamo detainee accused of terrorism a fair trial.

Following the Supreme Court's landmark decision legalizing gay marriage, Scalia cited his long-held belief that the Constitution should be followed as it was originally written.

"This practice of constitutional revision by an unelected committee of nine, always accompanied (as it is today) by extravagant praise of liberty, robs the People of the most important liberty they asserted in the Declaration of Independence and won in the Revolution of 1776: the freedom to govern themselves," he wrote.

The influential conservative judge was the first Italian-American selected to the country's highest court and held the position since 1986, when President Ronald Reagan tapped Scalia to succeed incoming Chief Justice William Rehnquist.

His first stint in Washington came between 1971 and 1977, first by being appointed General Counsel for the Office of Telecommunication Policy under President Richard Nixon -- which paved the way for the cable industry -- then by serving as Assistant Attorney General for the Office of Legal Counsel for Nixon and President Gerald Ford.

"For almost 30 Justice Antonin 'Nino' Scalia was a larger than life presence on the bench. Brilliant legal mind with an energetic style and incisive whit, and colorful opinions," said President Obama, speaking from Rancho Mirage, Calif. "He influenced a generation of judges, lawyers, and students, and profoundly shaped the legal landscape."

Obama said it is his constitutional duty to appoint a new judge. He will then leave it to the Senate to fulfill their responsibility of giving his choice a fair hearing.