WSM went ahead in the 14th and 19th minutes on goals by Jean Marie Mwanga and Santa Clara-bound Erik Hurtado, but DSC equalized through Shawn Ferguson and Juan Velasquez and won on the North Carolina-bound Martinez's goal in the 69th minute.
The game turned when WSN's Patrick DeYoung received a red card for a head butt in the 20th minute with the Oregon team ahead.
DSC is seeking to bring a national championship back to South Carolina for the first time. WSM would the second team from Oregon to win a U.S. Youth Soccer championship.
The National League champion Lower Merion Velez of Pennsylvania pulled away from Kentucky powerhouse Javanon, 4-1, to win its opening game in the under-17 boys competition in Lancaster, Mass.
A minute after Javanon took the lead, Lower Merion equalized on a goal by Jonathan Dolezal. Velez then pulled ahead on a goal by Kevin Israel, and Voltaire Escalona put the game away with two second-half goals.
Javanon's U-18 entrant fared better, beating the East Fishkill (N.Y.) Thunder, 3-1.
The Hicksville Strikers exploded for five goals -- the most goals scored by a boys team on Day 1 -- to beat South Carolina's other boys finalist, CESA Premier, in under-17 play.