"Happiest Birthday to my sweet @hilarieburton," Bush, 34, began her note. "Sister! We've been through a lot. At least 374 hair colors together. Crushes. Heartbreaks. Hangovers. Halloweens. Tears and laughter. Fear and joy. Successes and burn-it-to-the-ground failures. We've fought like rams and loved like family."
WILMINGTON - MARCH 19: Sophia Bush, star of 'One Tree Hill' cheers for her team during the charity football game on March 19, 2004 in Wilmington, North Carolina. The cast and crew of the WB drama are playing to raise money for Pop Warner scholarships. (Photo by Logan Mock-Bunting/Getty Images)
Sophia Bush (Photo by John Sciulli/WireImage for Bragman Nyman Cafarelli)
Sophia Bush (Photo by Gregg DeGuire/WireImage)
NEW YORK - JULY 15: (U.S. TABS OUT) (L-R) Actress/musician Hilary Duff, actor Chad Michael Murray and his fiance Sophia Bush appear on stage during MTV's Total Request Live at the MTV Times Square Studios July 15, 2004 in New York City. (Photo by Scott Gries/Getty Images)
Sophia Bush (Photo by Chris Weeks/WireImage)
Sophia Bush during Gen Art's Fresh Faces of Fashion at Santa Monica Airport Hanger 8 in Los Angeles, California. (Photo by Todd Williamson/FilmMagic)
Sophia Bush during Olympus Fashion Week Fall 2005 - Vera Wang - Backstage and Front Row at Bryant Park Tents in New York City, New York, United States. (Photo by Gregory Pace/FilmMagic)
LOS ANGELES - JANUARY 5: Actress Sophia Bush arrives at the premiere of Walt Disney Pictures' 'Glory Road' at the Pantages Theatre on January 5, 2006 in Los Angeles, California. (Photo by Michael Buckner/Getty Images)
(EXCLUSIVE, Premium Rates Apply) Sophia Bush (Photo by E. Charbonneau/WireImage for Focus Features)
Sophia Bush (Photo by Steve Granitz/WireImage)
Sophia Bush and Kevin Zegers during Sophia Bush and Kevin Zegers on Set of 'The Narrows' - May 24, 2007 at SoHo in New York City, New York, United States. (Photo by James Devaney/WireImage)
Sophia Bush (Photo by Jon Kopaloff/FilmMagic)
Sophia Bush (Photo by E. Charbonneau/WireImage)
(EXCLUSIVE, Premium Rates Apply) UNIVERSAL CITY, CA - AUGUST 26: Actor Jonah Hill, actress Sophia Bush, actor Christopher Mintz-Plasse and actor Michael Cera at the 2007 Teen Choice Awards at Gibson Amphitheater on August 26, 2007 in Universal City, California. (Photo by Kevin Mazur/WireImage)
NEW YORK - FEBRUARY 02: Actress Sophia Bush (2nd-L) sits in the front row of the Abaete Fall 2008 fashion show during Mercedes-Benz Fashion Week Fall 2008 at The Salon at Bryant Park on February 2, 2008 in New York City. (Photo by Stephen Lovekin/Getty Images for IMG)
NEW YORK - FEBRUARY 08: Actress Sophia Bush leaves the Marc Jacobs Fall 2008 fashion show during Mercedes-Benz Fashion Week Fall 2008 at the New York State Armory on February 8, 2008 in New York City. (Photo by Gustavo Caballero/Getty Images)
Sophia Bush and Minka Kelly
LOS ANGELES, CA - JANUARY 10: Actress Sophia Bush arrives at the Art of Elysium's 2nd Annual Black Tie Charity Gala 'Heaven' at Vibiana on January 10, 2009 in Los Angeles, California. (Photo by Jon Kopaloff/FilmMagic)
LOS ANGELES, CA - APRIL 30: Actress Sophia Bush arrives at the premiere Of Paramount's 'Star Trek' on April 30, 2009 at Graumanï¿½s Chinese Theatre, Hollywood, California. (Photo by Frazer Harrison/Getty Images)
PASADENA, CA - AUGUST 03: Sophia Bush arrives at the 2009 TCA Summer Tour - CBS, CW and Showtime All-Star Party at the Huntington Library on August 3, 2009 in Pasadena, California. (Photo by Jean Baptiste Lacroix/WireImage)
LOS ANGELES, CA - OCTOBER 11: Actress Sophia Bush arrives at Hollywood Life's 6th Annual Hollywood Style Awards held at the Armand Hammer Museum on October 11, 2009 in Los Angeles, California. (Photo by John Shearer/WireImage)
NEW YORK - FEBRUARY 15: Actress Sophia Bush backstage at the Monique Lhuillier Fall 2010 Fashion Show during Mercedes-Benz Fashion Week at the Promenade at Bryant Park on February 15, 2010 in New York City. (Photo by Jason Kempin/Getty Images for IMG)
LOS ANGELES, CA - SEPTEMBER 25: Actresses Lea Michele and Sophia Bush attend PETA's 30th Anniversary Gala and Humanitarian Awards at The Hollywood Palladium on September 25, 2010 in Los Angeles, California. (Photo by Jeff Kravitz/FilmMagic)
NEW YORK, NY - DECEMBER 06: Actor Sophia Bush attends the 2010 Global Green USA Sustainable Design Awards at Pier 60 on December 6, 2010 in New York City. (Photo by Mark Von Holden/Getty Images)
SANTA MONICA, CA - JUNE 18: Actors Austin Nichols and Sophia Bush attend Montblanc Presents The 24 Hour Plays LA at The Broad Stage on June 18, 2011 in Santa Monica, California. (Photo by Mark Sullivan/Getty Images For Montblanc)
NEW YORK, NY - SEPTEMBER 12: Actress Sophia Bush attends the premiere of The Weinstein Company's 'I Don't Know How She Does It' after party sponsored by QVC & Palladium Jewelry at Hudson Hotel on September 12, 2011 in New York City. (Photo by Stephen Lovekin/Getty Images for The Weinstein Company)
LOS ANGELES, CA - JANUARY 05: (L-R) Executive producer Joe Davola, actor Paul Johansson, actress Sophia Bush and creator Mark Schwahn pose at The CW's presentation of 'An Evening with One Tree Hill' at the Arclighht Theater on January 5, 2011 in Los Angeles, California. (Photo by Kevin Winter/Getty Images)
HOLLYWOOD, CA - FEBRUARY 08: Actress Sophia Bush arrives at the Los Angeles Premiere 'This Means War' at Grauman's Chinese Theatre on February 8, 2012 in Hollywood, California. (Photo by Jon Kopaloff/FilmMagic)
NEW YORK, NY - JUNE 04: Sophia Bush attends 2012 CFDA Fashion Awards Offical After Party at Boom Boom Room on June 4, 2012 in New York City. (Photo by Kevin Mazur/WireImage)
LOS ANGELES, CA - JULY 29: (L-R) Actors Sophia Bush, David Krumholtz, writers/executive producers David Kohan, Max Mutchnick, actors Michael Urie, and Brandon Routh speak at the 'Partners' discussion panel during the CBS portion of the 2012 Summer Television Critics Association tour at the Beverly Hilton Hotel on July 29, 2012 in Los Angeles, California. (Photo by Frederick M. Brown/Getty Images)
WEST HOLLYWOOD, CA - AUGUST 09: Sophia Bush attends the Elle Magazine And Sarah Hyland Hosts Songbirds' 'Miss Me' Album Release Party at Sunset Marquis Hotel & Villas on August 9, 2012 in West Hollywood, California. (Photo by JB Lacroix/WireImage)
WEST HOLLYWOOD, CA - SEPTEMBER 18: Actress Sophia Bush arrives at the CBS 2012 fall premiere party at Greystone Manor Supperclub on September 18, 2012 in West Hollywood, California. (Photo by Gregg DeGuire/WireImage)
SANTA MONICA, CA - APRIL 10: Actress Sophia Bush carrying Coach, attends Coach's 3rd Annual Evening of Cocktails and Shopping to Benefit the Children's Defense Fund hosted by Katie McGrath, J.J. Abrams and Bryan Burk at Bad Robot on April 10, 2013 in Santa Monica, California. (Photo by Donato Sardella/Getty Images for Coach)
NEW YORK, NY - JUNE 19: Sophia Bush attends the Target FEED Collaboration launch at Brooklyn Bridge Park on June 19, 2013 in New York City. (Photo by D Dipasupil/FilmMagic)
WESTWOOD, CA - AUGUST 10: Actress Sophia Bush attends the 1st Annual Founders Party for the Invisible Children's 4th Estate Leadership Summit at Royce Hall, UCLA on August 10, 2013 in Westwood, California. (Photo by David Livingston/Getty Images)
CHICAGO, IL - FEBRUARY 19: Sophia Bush appears in advance of a panel discussion at the Museum of Broadcast Communications in Chicago, IL on February 19, 2014 (Photo by Timothy Hiatt/Getty Images)
LOS ANGELES, CA - APRIL 20: Sophia Bush is seen on April 20, 2014 in Los Angeles, California. (Photo by GONZALO/Bauer-Griffin/GC Images)
LAS VEGAS, NV - SEPTEMBER 20: Actress Sophia Bush attends the 2014 iHeartRadio Music Festival at the MGM Grand Garden Arena on September 20, 2014 in Las Vegas, Nevada. (Photo by Isaac Brekken/Getty Images for iHeartMedia)
LOS ANGELES, CA - JANUARY 24: (L-R) Actors Jesse Tyler Ferguson, Sophia Bush and Sarah Hyland attend Entertainment Weekly's celebration honoring the 2015 SAG awards nominees at Chateau Marmont on January 24, 2015 in Los Angeles, California. (Photo by Christopher Polk/Getty Images for Entertainment Weekly)
LOS ANGELES, CA - FEBRUARY 13: Sophia Bush is seen in Los Angeles on February 13, 2015 in Los Angeles, California. (Photo by Bauer-Griffin/GC Images)
LOS ANGELES, CALIFORNIA - MAY 06: Sophia Bush seen out for dinner on May 6, 2015 in Los Angeles, California.
PHOTOGRAPH BY Candid / Barcroft Media (Photo credit should read Candid / Barcroft Media via GC Images)
NEW YORK, NY - JUNE 17: Sophia Bush is seen in New York City on June 17, 2015 in New York City. (Photo by Nancy Rivera/Bauer-Griffin/GC Images)
NEW YORK, NY - SEPTEMBER 26: Actress Sophia Bush speaks on stage at the 2015 Global Citizen Festival to end extreme poverty by 2030 in Central Park on September 26, 2015 in New York City. (Photo by Theo Wargo/Getty Images for Global Citizen)
NBCUNIVERSAL EVENTS -- 'NBC Chicago Celebration' -- Pictured: Sophia Bush, 'Chicago P.D.' at Cinespace Chicago Film Studios on November 9, 2015 -- (Photo by: Elizabeth Sisson/NBC/NBCU Photo Bank via Getty Images)
NEW YORK, NY - MARCH 08: Actress Sophia Bush is seen on March 8, 2016 in New York City. (Photo by ESBP/Star Max/GC Images)
PARK CITY, UT - JANUARY 22: Sophia Bush wears Sorel Around Park City - Day 1 2016 Park City on January 22, 2016 in Park City, Utah. (Photo by Jason Merritt/Getty Images for Sorel)
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"It's such a thrill to be in this place with you, 14 years after we first met and danced too late in bars -- still giddy that we were finally 21 -- and to watch you shine. You're a champion for your community. An incredible mom. You're the alpaca whisperer. You're whip smart and razor sharp and deeply tender," she continued. "There is no one I would have rather been on the world's most insane roller coaster with. And I'm so glad there's evidence that we both used to overpluck our eyebrows, undeniably, on the internet forever. At least we're not alone."
"I love you mama," Bush concluded. "#Breyton4eva #BreytonFeels #ShesMine #BetterInRealLife."
Because Bush and Burton literally ARE Brooke and Peyton, the birthday girl responded with her own sweet message about their friendship.
"You are just........the prettiest inside and out. I love the wild women we've evolved into TOGETHER," Burton replied. "Thank you for unconditional friendship and for being my style icon!!!! Seriously Soph. You're magic. I love you. Xxxxxxxx."
ET caught up with James Lafferty last year, who revealed that he's already got some ideas for a One Tree Hill revival.
"Nathan's gone back into basketball, coaching in the NBA," he brainstormed. "Haley's got an incredible music career. Jamie, I think, is on his way to the NBA and then maybe there's a few more, like 14 more, Scott kids coming through the pipeline."