Harlingen's strategic location at the intersection of U.S. highways 77 and 83 in northwestern Cameron County fostered its development as a distribution, shipping, and industrial center. In 1904 Lon C. Hill envisioned the Arroyo Colorado as a commercial waterway. He named the town he founded on the north bank after a city in Holland. The town's post office was established that year. The first school opened with fifteen pupils in 1905 near the Hill home, the first residence built in Harlingen. Harlingen was incorporated on April 15, 1910, when the population totaled 1,126. In 1920 the census listed 1,748. The local economy at first was almost entirely agricultural. Major crops were vegetables and cotton.
World War II military installations in Harlingen caused a jump in population from 23,000 in 1950 to 41,000 by 1960. Harlingen Army Air Field preceded Harlingen Air Force Base, which closed in 1962. The city's population fell to 33,603 by 1972, then climbed to 40,824 by 1980. Local enterprise, focused on the purchase and utilization of the abandoned base and related housing, laid the groundwork for continuing progress through a diversified economy. The estimated population in July 1985 was 49,000, of which about 80 percent was Hispanic. In the late 1980s income from tourism ranked second only to citrus fruit production, with grain and cotton next in order. The addition of wholesale and retail trade, light and medium manufacturing, and an array of service industries has broadened the economic base. Large-scale construction for multifaceted retirement communities is a new phase of industrial development.
The city of Harlingen operates a busy industrial airpark where bombers used to land. At Valley International Airport the Confederate Air Force occupied hangar and apron space until 1991. The first hospital in Harlingen was opened in 1923 and consisted of little more than two barracks as wings. The Valley Baptist Hospital was built nearby a few years later, and eventually the older hospital closed. The Valley Baptist Hospital has grown into the Valley Baptist Medical Center. The city's outstanding network of health care specialists and facilities parallels the growth of the still-expanding center. Also serving regional health needs are the South Texas State Chest Hospital, the State Hospital for Children, and the Rio Grande State Mental Health and Mental Retardation Center.
Besides public and church-affiliated schools, Harlingen students attend the University Preparatory School, the Marine Military Academy, Texas State Technical Institute, or Rio Grande Vocational and Rehabilitation Classes. Civic and cultural development in Harlingen has kept pace with the growth of the community. Fraternal orders and civic organizations operating in the community include Rotary, Kiwanis, Lions, Optimist, 20–30, VFW, and American Legion; a woman's building is maintained as a center for the activities of the many women's clubs active in the city. Development and appreciation of the fine arts are encouraged by organizations such as the Rio Grande Valley Art League, the Art Forum, and the Rio Grande Valley Civic Association, which stages its winter concert series at the 2,300-seat Harlingen Municipal Auditorium. Each March Harlingen is the site of the Rio Grande Valley International Music Festival. The city has two newspapers—the Harlingen Press, a weekly paper established in 1951, and the Valley Star, a daily established in 1911. In 1990 the population was 48,735. In 1992 the city was named an All-America City, cited especially for its volunteer spirit and self-help programs. In 2000 the community had 57,564 inhabitants and 2,549 businesses.