From the end of the 19th century onwards, Khorramshahr developed into Iran’s major commercial harbor. This development was a result of the excellent navigability of the river, with a draft for shipping of up to nine meters. Its development, however, was hampered by both geographical and historical factors. Geographically, the function of the Shatt al-Arab (q.v.) as a boundary between the Ottoman Empire and Persia in the 19th and early 20th century, and later between Iran and Iraq, caused recurrent conflicts. The 1914 Mixed Commission decided that the left bank of the low-water line of this tidal river be the international boundary (see BOUNDARIES i), which in effect gave control to Iraq over Iranian and Iranian-bound navigation. It should be noted, however, that the term Shatt al-Arab is no longer accepted by Iran. Under Pahlavi rule, it was replaced by the geographical term Arvand-Rud (q.v.). It was only in 1975 that a final agreement was reached, according to which the line of deepest water (the thalweg) became the internationally acknowledged boundary line. In spite of this clear definition, conflicts culminated in the Iraq-Iran war (see IRAQ vii) from 1980 onwards, when Iraq claimed Ḵuzestān as part of its own territory and invaded Iran. Both Khorramshahr and the oil city of Ābādān (q.v.) were among the first targets of the Iraqi invasion and were totally destroyed. The most telling indicators for the ups and downs of Khorramshahr’s development in the second half of the 20th century are its population figures (SCI, Table 3-10): 43,850 inhabitants (1956), 88,536 (1966), 140,490 (1976), unknown (1986, when the city was destroyed and abandoned), 34,750 (1991), 105,636 (1996), 125,859 (2006), 129,418 (2011), and 133,097 (2016).

While there seem to have been a number of earlier settlements on the site, the political and economic importance of Khorramshahr only dates back to the 19th century, when European powers competed in the establishment of military and trading posts along the coasts of the Persian Gulf. One of the most important locations became Moḥammara, the predecessor settlement of Khorramshahr. It was mainly due to its strategic location that Moḥammara became for a short time in 1820 the headquarters of a British Residency (later moved to Basra [q.v.] in today’s Iraq). Geopolitics and commercial interests remained at play in the following decades: In the first half of the 19th century, Moḥammara changed its political and territorial adherence several times between the Ottoman and Persian Empires until the Treaty of Erzerum (1847) allotted Moḥammara definitively to Persia. The strategically favorable location of Moḥammara at the crossroads of Persian Gulf navigation and the inland waterways has been emphasized again and again. In 1851, Keith E. Abbott, British consul in Tehran (1841-68), observed in his “Report on the Commerce of the South of Persia” that “the anchorage there is admirable and … there is water sufficient for vessels of 600 Tons burthen, or at any rate for any vessel that could cross the bar at the head of the Gulf … The situation of this place for the transit trade with the interior of Persia is in many respects good, its chief disadvantage is in the navigation at the head of the Gulf, near the entrance to the river, where extensive shallows and a dubious passage are always more or less attended with difficulty and danger, even to native navigators well acquainted with it. When once landed at Mohummereh, the transit of goods inland to the heart of Persia would be somewhat shorter than by Bushire, but not so much so as to be a subject of great consideration; though there is water carriage to Shooshter [Šuštar]” (Abbott, pp. 90-91). In 1856-57, British ships steamed the Karun River between Moḥammara and Ahvāz (q.v.) proving the navigability of the river, which was to become a major artery for the commerce between Great Britain and Persia. However, it was not until 30 October 1888 that the Persian government finally opened the Karun river (q.v.) as an international waterway. This date can be regarded as the starting point for the “modern” development of Moḥammara/Khorramshahr.

George N. Curzon (q.v.) noted in 1890 that the Karun flowed into the Shatt al-Arab about twenty miles below Basra by means of the Ḥaffār canal, which had been constructed “presumably … to promote trade between Arabistan and the then existing predecessors of the Turkish ports of Busrah and Baghdad” and that “the town of Mohammerah is situated a little more than a mile up the canal, on its right bank…” (Curzon, 1890, p. 515). He also gave a vivid description of Moḥammera itself. He described in detail his problems of reaching the place due to the intervention of Turkish customs. Thus he reports on another occasion that his “British India steamer,” stopping at the mouth of the Shatt al-Arab, was investigated: “At Fao the Turkish Custom-house officer had come on board, and it was thought likely that he might raise an objection to the vessel stopping at Mohammerah, to allow of my leaving her, although he could have no legal claim whatever to do so; Mohammerah being a Persian port, and the Turks having no right of control either over the boats of the British India Company or over the opposite side of the Shat-al-Arab” (Curzon, 1892, II, p. 337). As for the town itself, he noted that “those who, from the glowing accounts in the newspapers three years ago, formed a roseate conception of Mohammerah as a great trading emporium, will be disappointed to hear that it is a small and exceptionally filthy place with a ruined fort, a little over 2,000 inhabitants … and as yet only an insignificant foreign trade” (Curzon, 1892, II, p. 338). He claimed that its economic importance was rather limited, being only “a local mart for the needs of the Arab tribes, and for a limited export of native produce, such as grain, opium, wool, and dates” (Curzon, 1892, II, p. 340).

Nonetheless, the opening of the Karun River as an international waterway was followed by a rush of European, especially British, trading companies, in attempts to gain access to the Persian market (see KARUN RIVER iii. THE OPENING OF THE KARUN). Thus, Moḥammara developed into a major transshipment center. Curzon observed that after “the concession was finally granted, and the firm of Messrs. Lynch detached a boat from their Tigris flotilla, to run at regular intervals from Mohammerah to Ahwaz …,” the route was then improved “by the lately accorded permission for a steamboat to navigate the upper river from Ahwaz to Shushter [Šuštar] in correspondence with Messrs. Lynch’s steamers on the lower river, and by the expected commencement of a wagon road under the auspices of an English company, from Ahwaz to Tehran….” (Curzon, 1890, pp. 514-15). The construction of the wagon road (Lynch-Road) between Moḥammara and Ahvāz shortened the travel time and distance between the Persian Gulf and Tehran considerably. Thus, it developed into a serious competitor for other Persian ports (Bušehr, Bandar-e Lenga, and Bandar ʿĀbbās; qq.v.). In 1912-13, the Lynch Company operated three steamboats and seven barges with a capacity of 80-100 tons each on a weekly basis between Moḥammara and Ahvāz (Litten, p. 66). In view of these developments, and in connection with the discovery and exploitation of oil in nearby Masjed(-e) Solaymān in 1908, it may not be difficult to understand Moḥammara’s growth to one of the leading cities in Ḵuzestān (at that time still called ʿArabestān/Arabistan). Thus, the Military Report
on Arabistan (Simla) called Moḥammara “the capital and most important town of Southern ʿArabistan” and “the sole seaport and entrepot of foreign trade in all ʿArabistan”; according to its description of the town, “The native houses begin some 1¼ miles above the confluence of the Haffār and the Shatt-al-’Arab, and the frontage of the town extends upwards from that point, between which and the Shatt-al-’Arab are the new offices and bungalows of the Anglo-Persian Oil Company… . The town, which is constantly increasing in size consists at present of about 1,500 houses. Upon the river are some fine modern buildings; among the most conspicuous are the offices and residential houses of the Anglo-Persian Oil Company, and the palatial mansion of Haji Muhammad ʿAli, Rais-ut-Tujjar. There are 8 mosques, 3 public baths and 4 main bazaars, the Shaikh Khazʿal bazaar, which was widened and improved in 1921, the Suq-al-Shatt, Suq-al-Bedah (i.e., piece goods), and the Suq-al-Khadarah (meat bazaar). The town itself is divided into 4 quarters, Seef quarter, consisting of brick houses, Subba of mud huts and serifash, the Town, one-third of which are mud and two-thirds brick houses and Sabakh, in which all houses are of mud. Two-thirds of the town belongs to the Shaikh of Muhammarah and one-third to Haji Rais. The state of the town in spite of its modern improvements is still highly insanitary, the only kind of drain being a channel cut down the centre of each street. In the town towards its eastern end are the residence of the Persian ‘Karguzar’ and the Telegraph office” (Military Report on Arabistan, pp. 53-54).

In spite of the nominal sovereignty of the Persian government, the region of Moḥammara maintained a far-reaching autonomy under the leadership of local Arab shaikhs, who had established a kind of shaikhdom of Moḥammara. It was not until the end of the Qajar dynasty and the interim rule of Reżā Khan as commander of his famous Cossack Brigade (q.v.) that the territorial membership and integrity of the province of ʿArabestān to Persia was established beyond any political, military, and administrative doubts. After the accession to the throne, Reżā Shah Pahlavi pursued with vigor the complete and all-embracing integration of the oil-rich province, with its strong portion of Arab population, into the Persian state. The official new naming of former ʿArabestān to Ḵuzestān and, in 1937, the renaming of Moḥammara as Khorramshahr are testimonies to the “Iranization process.” Also, the construction and completion of the Trans-Iranian Railway with Khorramshahr as one of its southern terminals (completed during World War II as a feeder-line from Ahvāz) promoted Khorramshahr’s urban growth and economic importance (Melamid). At the close of World War II, the capacity of its harbor was approximately 250,000 tons. For 1967, storage capacities of 80,000 m² in warehouses and of 230,000 m² in open-air facilities were reported. In the mid-1960s, Khorramshahr’s imports and exports were calculated at 1,200,000 and 300,000 tons respectively (without oil and oil products), which gave it the unquestioned leadership among Iran’s commercial harbors (Kortum). Subsequently, however, a dramatic shift occurred due to the development of new port facilities, especially in Bandar-e ʿAbbās, Bušehr, and other locations along the coasts of the Persian Gulf. The Iran-Iraq war (see IRAQ vii. IRAN-IRAQ WAR) accelerated this process. Due to Khorramshahr’s location right on the border with Iraq and its function as one of Iran´s major seaports, Khorramabad was one of the first Iranian cities to be attacked and destroyed during the Iraq-Iran war. Captured by Iraq after fierce fighting between September and November 1980, it was finally reconquered by Iranian troops in May 1982. Subsequent to the war, Khorramshahr has been of only minor importance for international shipping, although a recovery process since 1988 has been undeniable. In spite of the fact that the harbor’s importance has declined considerably, the city’s population at the time of the 2016 national census was 133,097.