"I think we might have made a little bit of history tonight," leader Rachel Notley told her supporters Tuesday night. "Friends, I believe, that change has finally come to Alberta. New people, new ideas and a fresh start for our great province."
The Wildrose Party will be the province's Official Opposition, and party leader Brian Jean has been elected in his riding of Fort McMurray-Conklin.
The long-governing PC Party dropped to third place. The outgoing premier Jim Prentice told his supporters late Tuesday that he had resigned as party leader and had resigned his seat.
"My contribution to public life is now at an end," Prentice said.
The NDP won just over 40 per cent of the popular vote, the Wildrose got 24 per cent and the PCs were at about 28 per cent — roughly what was reported by many pollsters in the run-up to the election.
Rachel Notley to be Alberta's new premier
NDP Leader Rachel Notley will be Alberta's next premier. Her campaign has been said to have "shades of Jack Layton."
The NDP's previous best showing in Alberta was back in 1986 when the party took 16 seats, but by 1993 the party was shut out of the legislature.
Alberta is traditionally Canada's most conservative province, but anger at the long-governing Progressive Conservative Party seems to have spurred an orange wave that has swept over most parts of the province.
A party has to win 44 seats to get a majority. At 10:44 p.m. MT, the NDP was elected or leading in 54 ridings.
Jim Prentice called the election in April with 70 out of the 87 seats in the legislature. It was touted as a coronation for Prentice, once a Conservative MP recruited to fix the party's woes following the resignation of Alison Redford.
He had asked Albertans to give him a mandate after bringing in a "bad-news" budget when the election was called.
But over the campaign, there was a shift in momentum. It became a three-way horse race between the PCs, Wildrose and NDP.
Notley a leader 50 years in the making- Follow our live blog as reporters tweet from the field
Notley was born with orange roots.
Her father Grant Notley was the provincial NDP leader from 1968 until he was killed in a plane crash in 1984.
After Brian Mason resigned as NDP leader last year, Notley easily defeated her opponents, NDP MLA David Eggen and candidate Rod Loyola, winning 70 per cent of the vote.
The NDP is leading or elected in the majority of Calgary's ridings — areas where the PCs were supposed to hold onto power.
The party is also on the verge of sweeping the provincial capital, and has also made gains in rural northern Alberta.
Alberta Party wins seat
Alberta Party Leader Greg Clark secured his party its first seat ever in the provincial legislature.
Clark beat out former education minister Gordon Dirks in the riding of Calgary-Elbow.
It was a bad night for many of the cabinet ministers, as many lost their seats.
Albertans also punished the Wildrose floor-crossers in tonight's vote.