It also signals the beginning of a new era of development for the neighborhoods along the West Rail Corridor.
"The development that is sort of spurred on by this west rail line is just phenomenal," RTD General Manager Phil Washington said. "If you go on the west line, you see transit-oriented communities popping up everywhere. This is a tremendous, tremendous boom for the western part of this city."
The route, which starts at Union Station and ultimately ends at the Jefferson County Government Center, has 11 new stations and six park-and-rides.
The non-profit Urban Land Conservancy has been buying land and properties along the W - or West Rail Line - for the past six years. These investments - totaling $15 million - provide 600 units of housing (400 affordable), more than 50,000 feet of commercial space and a new Denver Public Library within walking distance of the lines.
"Each new rail line is a catalyst for transit-oriented development in metro Denver," said Aaron Miripol, pesident and CEO of ULC, in a news release. "ULC has been very strategic in our real estate investments and partnerships and stewardship on the W Line, maximizing and leveraging resources to increase economic opportunities for low-income families, seniors and the community as a whole."
The ULC estimates that this development has meant 500 new jobs.
Despite the benefits touted by officials, the W Line project continues to have its share of detractors, including the Colorado Independence Institute, who called it a "boondoggle."
They argue that the line could ultimately spell an increase in commute times for those who already use public transportation to travel between Golden and Denver, and that's its benefits for lower income users have been exaggerated.
"Look, it's a great day for people who have other transportation options but who think it would be cool to ride into downtown areas," said Mike Krause, VP of Operations for the Colorado Independence Institute.
"But for other residents, the people who RTD are supposed to be serving, basically what we're seeing today is an increase in their commute times."
W Line route map
While riding the W Line is free Friday and Saturday, trips will normally cost between $2.50 and $5 each way.
Krause argues bus lines, rather than a fixed light rail system , would have been more cost-efficient for Colorado tax payers, who approved FasTracks - which includes the W Line along with other mass transit projects - in 2004.
Some 9NEWS Facebook users argue that the new line's opening does nothing to help mass transit for people living on the north end of Denver.
"I question the RTD management and use of our money," Tom Martinez wrote in response to a 9NEWS post about light rail usage.
Others said the service is cost-prohibitive and inconvenient.
"I pay $9/day to ride and it takes me 45 minutes between parking in the back of full lots and the train ride," wrote Kristi Coffin. "If I drive downtown, it costs me between $9 to park and it shaves a full 15 minutes off of my time. So the cost versus convenience argument is meaningless to me."
Washington says the long-term benefits of the development outweigh the concerns its detractors have pointed to.
"This is well worth it," he said. "What we're talking about is moving more than 20,000 people a day - that's 20,000 cars off the road. This is infrastructure that will be here for the next 100 years."
Opening the route required adjusting existing bus routes, a process that RTD officials say is far from over.
"We'll go through these next three months, we'll see how everything works, but that doesn't mean we can't tweak things and change things in the next service change," said RTD Spokeswoman Daria Serna.
FasTracks is a 12 year, $6.5 billion public transportation plan, funded by a 0.4 percent sales tax increase that was implemented in 2004. It is the largest public mass transit plan in the country.
The W Line is the first project to officially open. Others include proposed light rail service to DIA, Longmont and Arvada.
"We compare this to the Super Bowl for RTD," Serna said. "...It's the opportunity to open a line, the first FasTracks line in the entire system, and we look forward to actually opening the rest of the lines approved by voters in 2004."