About 200 people attended the ceremony at the Midnight Sun recreation complex in Inuvik on Tuesday. The ceremony started with drumming and a prayer in both Gwich'in and Inuvialuktun.
Robert Alexie Jr, the president of the Gwich'in Tribal Council, was one of the first to speak.
"We don't have to fear devolution. It's a new beginning," he told the crowd.
Nellie Cournoyea, chair and CEO of the Inuvialuit Regional Corporation, said the implementation of devolution will be the biggest challenge for the territory.
"Anyone can go and shoot the head off a muskrat but who is going to clean it, gut it?" she said.
"I think that's the phase we are in. How do we go about the implementation? That's the most difficult part and that's going to take a lot of determination."
Aboriginal groups still must decide how to divide their 25% share of the royalties from resources.
N.W.T. Premier Bob McLeod signed for the territory, with Aboriginal Affairs and Northern Development Minister Bernard Valcourt for the federal government.
Regional leaders from five of the territory's seven aboriginal groups also signed on to the deal.
Negotiations on the deal concluded in March. MLAs voted to approve the deal earlier this month.
The territory still has to pass 24 pieces of new legislation, and shift 175 federal positions to the GNWT.
The agreement will take effect next April.
Former premier was confident this day would come
Inuvik Mayor Floyd Roland said he knew this day would come. He was the territory’s premier when the devolution agreement in principle was signed in 2011.
Roland said the biggest challenge at first was getting support from aboriginal groups.
"They helped us set the agenda on it, and it was August of that year prior to signing that I sat down with regional leaders here in Inuvik."
Initially, some felt the deal wasn't good enough, and said the territory should hold out for more. But Roland said that would have delayed devolution.
"So I knew at some point we would come to a place in our history to say, 'Is this agreement good to move forward or not?' To see the new government pick it up, continue on and stand behind the agreement in principle was good to see," he said.