Landour, a small cantonment town contiguous with Mussoorie, is about 35 km (22 mi) from the city of Dehradun in Dehradun district in the northern state of Uttarakhand in India. The twin towns of Mussoorie and Landour, together, are a well-known British Raj-era hill station in northern India. Mussoorie-Landour was widely known as the "Queen of the Hills". The name Landour is drawn from Llanddowror, a village in Carmarthenshire in southwest Wales. During the Raj, it was common to give nostalgic English, Scottish, Welsh or Irish names to one's home (or even to British-founded towns), reflecting one's ethnicity. Names drawn from literary works were also common, as from those by Robert Burns, Sir Walter Scott, Thomas Hardy, Robert Louis Stevenson and many others.

Landour is within Dehradun District of the former United Provinces. The United Provinces themselves were carved out of the former Northwest Province of the vast Bengal Presidency, which stretched from Burma to the Khyber Pass; accordingly, early accounts show Landour as part of "Bengal", which was technically true though the description was incomplete.

Landour was initially built by and for the British Indian Army. From 1827 when a sanatorium was built in Landour, the town was a convalescent station for the military, and hence much of Landour is a Cantonment. The original sanatorium is now occupied by the Institute of Technology Management ("ITM") of the DRDO; it is at the eastern end of the Landour ridge. In the early 20th century, a full British Military Hospital (BMH) was opened, with a medical staff that specialized in tropical diseases; the hospital closed soon after 1947. Also within the ITM premises is the former Soldiers' Furlough Home, a holiday home for British and Irish soldiers and JCOs in Indian regiments who lacked the means to return to Europe regularly. Or, the holidaying soldiers were serving in British regiments on rotation in India, their tours of duty lasting anywhere from 6 to 48 months. In terms of area, Landour Cantonment comprises about two-thirds of Landour; the remainder includes Landour Bazaar, which stretches along the spur that connects to Mussoorie.

The first permanent building in all of Mussoorie-Landour was also built in Landour in 1825. The house was built by Captain Frederick Young, the "discoverer" of Mussoorie, who was also the Commandant of the first Gurkha (or Gorkha) battalion raised by the British after prevailing in the Gurkha War. Young's house, "Mullingar" (hinting at his Irish blood), was the family home during the hot summers in the plains. Young's Dehradun-based battalion, then called the Sirmour (or Sirmoor) Rifles, was initially raised in a Gurkha POW camp in Paonta Sahib in Sirmour District – hence the name. The huge L-shaped building, with an outsized courtyard inside the bend of the "L", sits prominently atop Mullingar Hill in Landour Cantonment.

Among distinguished house guests at Mullingar in the early decades were Emily Eden (see below). Mullingar was expanded, changed hands several times and by the early 20th century had become the Mullingar Estate Hotel. During World War II, Mullingar was leased by the army to house the overflow of convalescing soldiers from the sanatorium, given the huge increase in war-related injuries. The hotel was bursting at the seams, as a number of British civilian evacuees from Burma, the Andamans, Manipur & Nagaland, which were occupied by Japanese forces, were also housed in Mullingar before being shipped out elsewhere. Mullingar finally fell into disuse after 1947 when Britons began to leave India, with the army already having vacated it after the postwar demobilization of 1945–46. The building soon fell into disrepair, occupied largely if not entirely by squatters (see below). A number of the families now living in Mullingar are Tibetan. Prayer flags flutter in the wind every day, and Losar celebrations are held in the courtyard every year.

The legal distinction between Mussoorie and Landour did not arise until the 1860s, when after the historic events of 1857 cantonments were properly surveyed and formalized. In particular, control of the ridge-lines and water sources was crucial, given rising British anxieties over their grip on India. The defensibility of garrisons was critical, especially in hill stations with large European populations. The Cantonments Act of 1924 further clarified the rights of the property owners; new construction of any kind, especially of private homes, was virtually banned. Conservation was also a key goal, given the excesses of the 19th century (see below); the Act clearly states that title to all trees remains with the army, hence there has been no logging in Landour since in over a century, as can be seen. By definition, all non-military and non-governmental buildings built after 1924 are 'illegal'. Therefore, there are few 'modern' homes in Landour, though renovations and reconstruction of pre-existing houses are permitted. Thanks to the 1924 Act, Landour Cantonment is—unlike Landour Bazaar—largely free of the commercialization that can be seen in much of Mussoorie proper, especially along the 'main drag' of Mall Road where tourists throng in the summer.

Racially, Landour was distinctly more European than Mussoorie. It was no accident. First, the army presence (albeit non-regimental) offered an excuse to 'keep out' Indians. Second, Maharajas were encouraged to build grand summer homes, but were directed towards Mussoorie. Among them were the ruling families of Kapurthala, Nabha, Alwar, Jind, Baroda, Kasmanda, Katesar, Kuchesar and other princely states. And this despite Maharajas being hand-in-glove with the Raj in terms of ruling the Indian masses; the former, who remained nominally 'autonomous', legitimized the rule of the latter. Tellingly, not a single princely residence was ever built in Landour. (The only 'exception' was The Castle, see below, but it was built by the British as a quasi-prison). Even the ruling family of Tehri-Garhwal (from whom the region was seized by the British) had no residence in Landour, though the family later did acquire some properties from Britons who sold out. These racial barriers, while quite real were more informal than formal; they began to weaken after World War I as the Indian freedom movement gained steam. The author Emily Eden, sister of the Governor-General Lord Auckland, wrote incisively about the biting racism of Britons towards all Indians (except Maharajas, whose over-the-top hospitality they craved), after spending much time in Landour, Shimla and Ooty in the late 1830s. Many Anglo-Indian families also put down roots in Landour, and in Barlowganj just below Mussoorie, in the 19th century. They were attracted in part by the schools, and by the sense of 'otherness' versus quotidian India. A handful remain, most having emigrated after 1947, but the few who remain (most are in their golden years) are treasure troves of local lore.

Indeed, the events of 1857 led to a spurt in the European population of Mussoorie-Landour, with many families leaving the 'exposed' towns of the Gangetic Plain. Among the Britons who thus moved to Landour were the parents of Jim Corbett. Both had lost their spouses, and would meet and remarry in Landour (see below). His mother had moved from Meerut, where her first husband had been killed in action in 1857. Thousands of Europeans, mostly Britons, are buried in the twin towns. The Cantonment has adjacent Protestant and Catholic cemeteries, though due to overcrowding in the former, the latter has of late become non-denominational – they are managed by the same committee. In 1901, the town had a population of 1720, which climbed up to 3700 in the summers, when the heat of the Indian plains became unbearable.