Smith's 132 was the cornerstone of his side's imposing total of 368 for three after winning the toss on the opening day of the four-match series.
Smith and Australians Ricky Ponting and Matthew Hayden have passed 1,100 Test runs this year, while West Indies captain Brian Lara and Smith's opening partner Herschelle Gibbs have reached 1,000.
"I'm not that interested in milestones like that," Smith told reporters after taking his year's total to 1,140 runs.
"It's not something I think about when I walk out to bat, but if it puts the team in a good position then that's fantastic."
Smith said his innings was not without difficult moments.
"I had to fight off a few demons in the 90s. My feet weren't moving that well when I started, but my hands were feeling good," Smith said.
West Indies bowled inconsistently on a hot day but Smith thought the tourists stuck to their task well.
"If they were to look at the way they bowled, I think they would say that they bowled too many four-balls," Smith said.
"They bowled long spells in the heat, and they just kept running in. I thought Merv Dillon bowled superbly."
Smith said South Africa were aiming for a total of 500-600 runs.
"We scored quickly today, and, hopefully, we can do so tomorrow," Smith said.
