Competing at Baywood Golf & Country Club in Arcata, Sundberg shot a 93 to edge Arcata’s Avery Meadows for the best round of the day by just one stroke.
The victory officially sealed the league title, although it has been a one-horse race for much of the season.
Sundberg claimed the championship by an impressive 59 strokes, and she walks away from the H-DNL having won a remarkable 12 of 14 rounds in league play over the past two seasons.
As a junior she clinched the league title by 63 strokes.
Arcata senior Sagen Sarchett also enjoyed a memorable H-DNL campaign and placed second overall with a season total of 597.
The race for second through fourth was tight, with just eight strokes separating three golfers over seven rounds of competition.
Eureka’s Illeah Brannon (602) finished just five strokes behind Sarchett, with Meadows (605) just three strokes further back in fourth.
Arcata’s Iris Coonrod (615) and Madyson Nelson (628) and St. Bernard’s Hannah Finck (645) rounded out the top-seven golfers, each of whom receives all-league recognition.
The Arcata girls won by an impressive 240 strokes, with Eureka second and McKinleyville in third.
Brannon and St. Bernard’s Allyson Hagler each shot a 98 on Monday to tie for the third-best round of the day, with Finck the only other golfer to break 100 on the day with a round of 99.
Coonrod (101), Arcata’s Amaya Urquidez (103), Sarchett (106), Del Norte’s Sophia Jagger (107), Nelson (111) and McKinleyville’s Neyr’res Bartoo (111) rounded out the top 11.
The Tigers will advance as a team, along with the other five best individuals in league play, a group that includes Sundberg, Brannon, Finck, Mia Lopez (Eureka) and Hagler.