That service will go from Culver City, along the Exposition Boulevard right-of-way, and on to Santa Monica.
There were some problems in the beginning; the first phase was costly and had many delays.
Construction on the first phase began in 2006 with a price tag of $640 million. That eventually jumped to $940 million. Transportation officials said the budget changes were due to dramatic increases in construction and material costs.
A groundbreaking ceremony was held for the "Expo Line Phase Two Project" on Monday, and officials hope the second phase will go more smoothly.
"We have a contingency now," said Expo Construction Authority CEO Rick Thorpe. "It was pretty small on phase one. Now on phase two it's much higher to take care of unknowns."
The second phase has a budget of $1.5 billion, and will continue west to the intersection of Colorado Avenue and 4th Street in downtown Santa Monica. It will take commuters straight to the beach.
"All of us who were stuck in traffic trying to get to this event will be reminded again of why we so desperately need this," said Darrell Clarke from the group Friends for Expo Transit.
Mayor Antonio Villaraigosa was at the ceremony and said while the line won't solve the Westside's traffic problems, it will ease them and also create jobs.
"When you look at the 9,000 to 10,000 jobs that will be created just with this phase alone, finally connecting downtown to Santa Monica," said Villaraigosa.
Once completed, commuters will be able to travel from downtown Los Angeles to Santa Monica in about 40 minutes.
The entire phase is expected to be completed in 2015.
Construction on the second phase will cause some traffic congestion in the coming months, particularly on Colorado Avenue.