Seattle Sounders sealed their second title in four seasons with a 3-1 home victory over Toronto FC in front of 69,274 fans at CenturyLink Field - the second highest attendance for an MLS game.

The on-loan Smith is the only Australian to win American soccer's top club prize.

Smith, in fact, became the first Australian to play in the decider - with Cahill, Danny Allsopp, David Carney, Andy Rose and Bernie Ibini all failing to achieve such success during their MLS stints.

On-loan left-back Smith started for Seattle but was replaced on 61 minutes.

The 25-year-old has been recalled to the Socceroos set-up by coach Graham Arnold and will join the squad this week for their November 15 World Cup qualifier against Jordan in Amman.

It's been quite a journey for Smith after he left Premier League giants Liverpool in 2016 in search of more first-team football.

He was loaned out to Swindon in 2014, had a frustrating time at Bournemouth, who remain his parent club, before his career got back on track when he linked up with Seattle in August last year.

Smith played in 29 games this MLS campaign, 26 as a starter, and has previously said he is open to making his Seattle stay a permanent one.

The Sounders repeated their 2016 final success over Toronto after a goalless first half.

Kelvin Leerdam's angled shot deflected in off Toronto's Justin Morrow on 57 minutes, substitute Victor Rodriguez connected in the 76th and Raul Ruidiaz added a third in the 90th.

Substitute Jozy Altidore scored a consolation goal for 2017 champions Toronto in stoppage time.

Seattle became the sixth franchise in league history with multiple titles.

The Sounders joined Houston, Sporting Kansas City and San Jose with two titles while Los Angeles Galaxy have five and DC United four.

Australian Associated Press