The contracts were completed Friday.
Ballard was let go by Vancouver earlier this week. He said he had interest from a half-dozen other teams but picked a two-year deal with the Wild because he believed he best fit with them on the ice. As a bonus, he's a native of Minnesota.
According to a person familiar with Spurgeon's contract, who spoke on condition of anonymity because the team did not release the value of the deal, Spurgeon will get just under $8 million over three seasons. His annual average value is $2.66 million.
AP Sports Writer John Wawrow in Buffalo, N.Y., contributed to this report.