Sound Transit board members gathered Wednesday on the elevated tracks in south Seattle to mark the milestone, using golden bolts to secure the last bit of track.

The tracks run from downtown Seattle to Tukwila Station near Sea-Tac Airport.

"We were completing that initial spine for light rail. I believe that when the trains are up and running on this initial spine, we will hear from communities all over the central Puget Sound region. They will be asking us to bring it to them," said board member Julia Patterson.

Service between Seattle and Tukwila is scheduled to begin in July of next year.

The track to Sea-Tac Airport is in the process of being laid, and service there is scheduled to begin in December 2009.