After 15 years of planning and permitting, construction will begin this year on the TransWest Express high-voltage transmission line - a milestone expansion of Wyoming's electric power export industry to markets in the American Southwest and one of the largest transmission upgrades to the western grid in decades.

The Bureau of Land Management granted TransWest Express LLC a "notice to proceed" in April, culminating years of work and millions of dollars invested in a "vision" to bring Wyoming's renewable energy potential to the rest of the West, according to company officials.

"It's a day th...