Jackson's time of 18:03.91 broke the previous record of 18:18 held by Hereford's Kristen Malloy.
Jackson held off Hereford senior Kelly Wesolowski (18:28.95) and Middletown's Reilly Caldwell (18:43.69) for the title.
"I was not surprised that the course record fell today," Dulaney coach Chad Boyle said. "Haley, Reilly and Kelly, with those three together providing that level of competition, I knew someone was going to break the record."
Jackson primed for the race by sleeping in the car on the way up from Calvert County.
During the pre-race walk she let her teammates wake her up.
"Before races we are just joking around during the course walk, listening to music together, like John Cena and Sponge Bob songs, and having our inside jokes," Jackson said. "It makes it so much easier to calm down and enjoy the race even more."
Second-place finisher Wesolowski made her antsy during the race.
"Seeing her that close, I got really excited and I was like, 'This is going to be a good year if she's that close.'" Jackson said.
Wesolowski was just happy to be on any course.
She played soccer her freshman and sophomore years and planned to switch to cross country for her junior year, but she had foot surgery.
"On Monday, we made a decision that I was going to race here, originally, I wasn't going to race here," said Hengst, who had planned on lightening up his racing schedule.
That rest will have to wait.
"On the starting line I felt pretty good," Hengst said. "I knew my legs were going to be fresh, but I was a little shocked by the fast pace I had to run today."
Hengst led from the start and finished ahead of Bel Air's Kieran McDermott (15:53.23) and Howard's Nick Deamer (16:01.60).
The top five finishers from the Dulaney boys team that won last year graduated, but the new Lions won the team title convincingly.
Dulaney (77) was well ahead of runner-up Howard (118) and third-place Mount St. Jospeh (126).
"We are building quite a legacy here," Boyle said. "It's a seamless transition."
Matt Owens (7th, 16:12.70) was the leader of the Dulaney pack.
'There is pressure," Owens said. "We've got to keep up the tradition, but they taught us really well and we've got great coaches and the team is filled with guys with great potential and we are all dedicated."
"Matt Owens stepped up and did a tremendous job," Boyle said. "We call it talking with his legs."
The rest of the top five for the Lions included Brian McCullough (12th, 16:44.89), Connor Martin (18th, 16:51.42), Alex Ozbolt (21st, 16:53.58), and Brendan O'Brien (23rd, 16:55.43).
"Brendan O'Brien, our number five runner, was running his first varsity race today and he ran a heckuva last mile," Boyle said. "I would say he passed 10 guys in the last mile."
The fourth-place Dulaney girls were led by the top 15 finishes of seniors Dorrie Gaeng (7th, 19:49.45) and Jessica Meek (11th, 19:59.12).
"Dorrie and Jessica are really doing a good job with a lot of young people who have never run before and we are going to be there," Boyle said.
Sophomore Brooke Ruffin (45th, 20:45.90), junior Destiny Clinton (35th, 21:12.61) and senior Julia Clark (45th, 21:36.67) rounded out the top five for the Lions.
The Towson girls finished fifth in the team standings, led by Karen Prem (10th, 19:57.24).
"She (Prem) had a break in outdoor track when she ran a 2:23 800 [meters)," coach Gil Stange said. "That inspired her summer training and she really dedicated herself to that and she's in great shape now."
Sydney Conboy (19th, 20:22.79) and Jaqui Sheedy (22rd, 20:31.79) placed in the top 25 and Lauren Miller (37th, 21:15.41) and Celia Parts (60th, 22:29.19) completed the top five for the Generals.
The seventh-place Towson boys were led by the fifth-place finish of senior Jon Ellis (16:09.50).
"He had a breakthrough outdoor season in the mile and two-mile," said Stange, noting he was a regional runner-up. "He and Sushan [Dhaurali] really worked hard over the summer."
Dhaurali was 17th (16:51.11), followed by Towson teammates Jack Morgan (60th, 17:52.85), Tyler Paul (68th, 18:01.33) and Vincente Iglesias (76th, 18:07.06).
The Hereford boys placed 12th. They were led by junior Dillon Coffey (34th, 17:03.26).
The Catonsville girls placed 10th out of 20 teams in the girls race.
They were led by sophomore Eva White (21st, 20:30.78).
The 14th-place Comet boys got a strong run from senior Graham Strzelecki (14th, 16:49.54).
Dulaney 82, Howard 118, Mount St. Joe 126, Mountain View 151, Century 179, Loyola Blakefield 204, Towson 221, Calvert Hall 278, Middletown 281, McDonogh 296.
Hereford 83, Howard 105, Century 115, Dulaney 122, Towson 144, NDP 152, Paint Branch 208, Mountain View 252, Bel Air 297, Catonsville 300.