Southwest scored one run in the second when sophomore Monique Skidmore singled and was driven home by hits from senior Megan Day and junior Debi Vining.
Lamar answered in the fourth with a run to tie the game at 1-1. The match remained scoreless going into the seventh.
Skidmore once again singled in the seventh. Freshman Stacey Hobbs entered the game as a courtesy runner and stole second. Vining bunted to score Hobbs from third.
Freshman Haley Clifton hit a single, got out at first but advanced the runner to third. Junior Megan Gillis drove in a third run, which was enough for Southwest to end the game at 3-1.
Freshman Megan Hendrix was the winning pitcher. She had six strike-outs and no walks.
Defensive standouts in the game included: Day with three assisted put-outs from third; junior Megan Gillis with two solo catches in center; and freshman Chelsea Sneed with a big catch in right field.
"We went into districts with a goal of obtaining our first district victory," said coach Ben Abramovitz. "Every night we set a new goal and made history one inning at a time. These kids figured out how to fight to the finish and win.
"This feat was a team effort that has instilled a desire to win in themselves that they never knew they had," Abramovitz added.
The district championship is a first for the school's softball program, and the team's accomplishment was witnessed by stands full of Southwest fans.
"This championship is one these kids will treasure forever," Coach Abramovitz said. "Thank you to all the students, faculty and community members that came out to support these athletes."
"What a ride for a small town group of girls who had never experienced anything past loading the bus after the first loss of district play to now playing in the sectional round of the state playoffs," Coach Abramovitz said.
Southwest will play Morrisville at Ash Grove tonight (Wednesday) at 5 p.m.
The Lady Trojans 2005 roster boasts six freshmen, three sophomores, three juniors and two seniors.
Players include: seniors Neely Wilson and Megan Day; juniors Debi Vining, Megan Gillis and Lindsey Hutson; sophomores Monique Skidmore, Brittany Clifton and Megan Hendrix; and freshmen Kelsey Henry, Porsche Cunningham, Stacey Hobbs, Chelsea Sneed, Mercedes Cunningham and Haley Clifton.
Season highlights, in addition to a district championship crown, include a first place finish in the Cassville Tournament and Southwest finishing first place in their pool at the Reeds Spring Tournament.
In advancing to the district championship game, the Lady Trojans defeated Purdy 2-0 and then upset first-seeded McAuley 3-1.