I see this term on a lot of different boats and have always wondered if it has significance or if it just looks cool.

(...now searching for my asbestos jacket, just in case)

Each of the SBI classes has different identifiers for the reigning national champ. For the superboat class, It's US-1. For the superboat vees, V-1.

This is the United States...US=1 just makes more sense than Canada-1 or Mexico-1...........

US-1 has it's origin with APBA. Traditionally, APBA Offshore awarded the US-1 designation to the national high points champion in the old Open Class, which used to align with UIM Class One.

I think it has something to do with who spent the most $$$$$

Hmmmm.....

I just thought it looked cool. I've never even been in a boat race but I will put it on the 28 Skater I'm going to build some day....just for looks

As Mike said, historically the title US-1 went to the APBA national champions of each year. In the Open class you were allowed to run the number US-1 for the worlds that year and the US-1 number all season the following year. It is prestigious in that manner and carries an honor to have it. Currently the Stihl Race team have it on there 388 Skater as they have won the title twice in a row.

The number is on you boat because Stuart Hayim whom built your boat was a national champion and earned the right to use it. As was Jim Lee's Freedom boat , ALSO one of Stuarts old boats. Putting US-1 on a 28' Skater would be ridiculous and IMO for anyone to put US-1 on any boat that did not EARN it by winning a national championship is a joke. Begin in the graphics business I personally do not care for people putting race numbers on pleasure boats. I believe it is asking for trouble and degrades true boat racing and racers. You want a number, earn it....

US1 was earned over a whole season, "World Champion" Over one weekend

Well said Ryan!