The school is the oldest operating high school in Loudoun County which opened in 1954. County has served a mostly rural population, and remained this way even after Loudoun Valley High School opened in 1963 in Purceville and then especially after Broad Run High School opened in 1969 and took sections in the more suburban eastern half of the county. However, as the growth of Loudoun County hit further west beginning in the 1980s, and because of rapid growth from that time on, most of County's population has become suburban. After over 45 years of sharing the central part of the county with Loudoun Valley, in 2000, after a large influx at Loudoun Valley, County sent most of its eastern Leesburg student base to Stone Bridge High School after its student body ballooned to 1,600 students from about 1,200 for most of the 1990s. Two years later, County fed the remainder of its eastern Leesburg student base into Heritage High School. In 2005, a small number of County students were relocated to Freedom High School and Briar Woods High School. In 2010, Tuscarora High School opened up and took County's Lucketts area students.
Mascot
The mascot for the school, the Raider, was named in honor of Mosby's Raiders. The mascot was chosen by a segregated student body in 1954. The original school seal depicted the Raider on horseback with a Confederate Battleflag in his hands. This logo was changed in 1980 to the current design in the face of racial criticism over the emblem. However, when the first new gym was built and the logos were painted on the floor, the original design was accidentally used and had to be removed and repainted. Attempts to remove the mascot were made in the 1970s and 1990s. Following the killing of George Floyd in 2020, alumni started a petition to change the mascot. On June 30, 2020, the Loudoun County School Board officially removed the mascot.
Murals
In 1957 murals that illustrate important events and times in Loudoun County's history were painted in the Auditorium by the Loudoun Sketch Club. Two subsequent murals were created, one in the 1970s, the other in 2004.
Renovations
County has undergone several renovations and expansions since it was opened. The first expansion occurred in 1966, with the addition of a Vocational Education Wing attached to the side of the front portion of the building. In 1976, a second gym space was added. In 1990, a new science wing and cafeteria were built in the back of the high school, which allowed the old cafeteria to become the new site of the current band and chorus rooms. One large problem with the science wing was that it was located upstairs from the cafeteria, but was unconnected to the rest of the school's second story. In 1996, a new main gymnasium and girls locker rooms were completed. The new gymnasium can carry about 1,300 people, and the old main gym became the auxiliary gymnasium. Six foundation based trailers were built to replace classrooms that were displaced by the project. In 1999, additional parking spaces were built around County because of the addition of eight temporary trailers that were placed on a faculty parking lot due to overcrowding; the trailers were moved to Loudoun Valley the next year when Stone Bridge opened. In 2002, two high school seniors set an assistant principal's office on fire, closing school for a week. Because of the fire's damage, the school had to replace its old-fashioned bell system with an electronic one that the other five high schools at that time used. The main office was renovated before the end of the 2001-2002 school year. In 2005, Loudoun County underwent its most extensive project in school history, an eighteen million dollar endeavor, which included the building of another auxiliary gym to replace the older one. The old auxiliary gymnasium turned into a new library, which used to be on the second floor. The library's area turned into a new section of classrooms, which eliminated the need for the six foundation based trailers. Additional classrooms were built adjacent to the science wing. Aerial walkways were built, connecting the separated second floors. The renovation was completed in late 2006. It is now one of four high schools in the Town of Leesburg. A renovation of the NJROTC building totalling 3 million dollars took place during the summer of 2017.
Segregation
County originally opened up as a segregated school for whites. Black students went to Douglass High School. In the 1968-1969 school year, County became fully integrated.
"America Day" incident
On the week of Friday, April 21, 2017, six senior students from Loudoun County High School's "Young Conservatives" club shared on social media that the LCHS school administration had rejected an America-themed "spirit day" for being "too political." The students then proceeded to post flyers around the school declaring the following Monday to be "America Monday," which were reportedly torn down by school officials. LCPS public relations officer later stated that the flyers were taken down because the students did not seek "permission to display them on school property." Following the reports by the club, other students, and an op-ed by Daniel Eisert to the LoudounNow newspaper, the administration received backlash on social media for the reported decision, and "America Monday" received support from parents, members of the school's "Young Democrats" club, and students from other schools. By the evening of Friday, April 21 the LCHS principal announced that the following Monday would be changed to "America Monday" in an email sent out to parents. On the following Monday, April 24 it was reported by ABC 7 News, Conservative Review, Red Alert Politics, and the Loudoun Times-Mirror that America Monday went on as planned and students were seen in red, white, and blue. The administration reported to ABC7 News that the students "didn't officially bring the idea" of America Monday to them, despite the Student Government bringing the idea to them several months prior. Additionally, the Conservative Review reported that the administration told them the idea was turned down because America-themed days had been held in the past, and they wanted a more "diverse mix of themes" despite an America-themed spirit day not held since at least 2010.
NJROTC
The NJROTC Program at Loudoun County High began in the 2009-2010 school year. The program draws from the entire county. The program is the first JROTC in Loudoun County, and is currently the newest program in the nation.
The average SAT score in 2006 for Loudoun County was a 1,582.
Athletics
Loudoun County offers a wide selection of fall, winter and spring sports including cross country, football, field hockey, golf, volleyball, basketball, gymnastics, swim, wrestling, baseball, crew, lacrosse, soccer, softball, tennis, hockey, and track. The raiders are known for an outstanding volleyball team, winning every state title since 2007. Other notable sports include the men and women's soccer team as well as the band program.
Athletic facilities
The raiders have a stadium which features a 400m track and a multipurpose AstroTurf field used for football, soccer, lacrosse and field hockey. Beside the stadium is a practice field on grass which has field goal posts and soccer nets. Other outside facilities include 6 tennis courts, a baseball field, a softball field and a marching band practice field. Inside is a main and auxiliary gym, as well as a weight room and wrestling/gymnastics facility.
State championships
Band
Loudoun County High School has a medium sized band program, which includes a symphonic band, concert band, two jazz bands, as well as a marching band called the Marching Raiders. The Loudoun County Raider Band has been a Virginia honor band every year since 2004, and the marching and concert bands have received superior ratings for the last 14 years. The marching band also won the 4A US BANDS National Championship in 2018 and 5A USBANDS National Championships with the highest score of all time in the A class division.
