TransCanada Corp., Canada’s largest pipeline company, won state approval and a $500 million subsidy to proceed with plans to build an estimated $27 billion pipeline that will carry natural gas from Alaska’s Arctic region to U.S. markets.

The Alaska Senate voted today in favor of the proposal by Calgary-based TransCanada, following approval last month by the House. The company will get a state license to begin studies and early work on the pipeline.

“We’ve been trying to get this pipeline for 30 years,” Alaska State Senator Hollis French said today. “This piece of legislation gets us there.”

The project was born out of an effort by Governor Sarah Palin to exploit gas deposits on Alaska’s North Slope that were discovered decades ago and stranded by the inability to get the heating and power-plant fuel to users. Palin solicited pipeline proposals last year and chose TransCanada’s after saying competing plans didn’t meet the state’s requirements.

We need it.