The Peter Jackson-directed Lord of the Rings prequel set a new December box office record in the process, beating the three-day earnings of The Lord of the Rings: The Return of the King, which scooped $73.3 million in 2003.
Disney animation Rise of the Guardians remained runner-up for a second week, with Lincoln climbing one place to three after receiving several nominations at both the Screen Actors Guild and Golden Globe Awards this week.
Last week's chart-topper Skyfall dropped to four, earning $7 million in its sixth week on release, while The Twilight Saga: Breaking Dawn - Part 2 also crashed three places to six with $5.175 million.
Life of Pi stayed steady at five, with Wreck-It Ralph, Playing for Keeps and Red Dawn all remaining to hold onto a top ten spot.
Silver Linings Playbook also climbed up one place to ten after also being honoured with a clutch of SAG and Golden Globe nominations.
The top ten in full (studio estimates):
1. (-) The Hobbit: An Unexpected Journey - $84.775 million
2. (2) Rise of the Guardians - $7.42 million
3. (4) Lincoln - $7.244 million
4. (1) Skyfall - $7 million
5. (5) Life of Pi - $5.4 million
6. (3) The Twilight Saga: Breaking Dawn - Part 2 - $5.175 million
7. (7) Wreck-It Ralph - $3.273 million
8. (6) Playing for Keeps - $3.247 million
9. (8) Red Dawn - $2.394 million
10. (11) Silver Linings Playbook - $2.084 million
Watch Digital Spy's interview with The Hobbit star Martin Freeman below:
Photo gallery - The Hobbit: An Unexpected Journey: