Aachen, in French, Aix-la-Chapelle, the name by which the city is generally known; in Latin Aquæ Grani, later Aquisgranum, is the capital of a presidency in Rhenish Prussia, and lies in a valley basin, surrounded by wooded heights, on the Wurm, a tributary of the Roer, on its way to the Meuse. Population, 1 December, 1905, 151,922 (including the Parish of Forst); Catholics, 139,485; Protestants, 10,552; Israelites, 1,658; other denominations, 227. The city owes its origin to its salubrious springs which were already known in the time of the Romans. There appears to have been a royal court in Aachen under the Merovingians, but it rose to greater importance under Charlemagne who chose it as his favourite place of residence, adorned it with a noble imperial palace and chapel, and gave orders that he should be buried there.
The precious relics obtained by Charlemagne and Otho III for the imperial chapel were the objects of great pilgrimages in the Middle Ages (the so-called "Shrine Pilgrimages") which drew countless swarms of pilgrims from Germany, Austria, Hungary, England, Sweden, and other countries. From the middle of the fourteenth century onwards, however it became customary to expose the four great relics only once in every seven years, a custom which still holds. These pilgrimages, the coronations of the German emperors (thirty-seven of whom were crowned there between 813 and 1531), the flourishing industries and the privileges conferred by the various emperors combined to make Aachen one of the first cities of the Empire.
The decay of Aachen dates from the religious strife of the German Reformation. Albrecht von Muenster first preached Protestantism there in the year 1524 but was afterwards forbidden to preach the new views and executed on account of two murders committed during his stay in the cities of Maastricht and Wesel. A new Protestant community was soon, however formed in Aachen, which gradually attained such strength as to provoke a rising in 1581, force the election of a Protestant burgomaster, and defy the Emperor for several years. The Ban of the Empire was, therefore, pronounced against the city in 1597 and put in force by the Duke of Julich, the Catholic overlord of the city. The Catholics were restored to their rights, and the Jesuits invited to Aachen, in 1600. In 1611, however, the Protestants rose afresh, plundered the Jesuit college, drove out the Catholic officials in 1612, and opened their gates to troops from Brandenburg. The Ban of the Empire was again laid on the city, and executed by the Spanish general, Spinola. The Protestant ringleaders were tried or exiled, and many other Protestants banished. These troubles, together with a great fire which destroyed 4,000 houses, put an end to the prosperity of the city.
Two treaties of peace were concluded at Aachen during the seventeenth and eighteenth centuries. By the first, dated 2 May 1668, Louis XIV was compelled, by the Triple Alliance between England, the Netherlands, and Sweden, to abandon the war against the Spanish Netherlands, to restore the Franche Comté, which he had conquered, and to content himself with twelve Flemish fortresses. The second treaty, dated 18 October, 1748, put an end to the War of the Austrian Succession. In 1793 and 1794, Aachen was occupied by the French, incorporated with the French Republic in 1798 and 1802, and made the capital of the Department of the Roer. By the terms of the French Concordat of 1801 Aachen was made a bishopric subject to the Archbishop of Mechlin, and composed of 79 first class, and 754 second class, parishes. The first and only bishop was Marcus Antonius Berdolet (b. 13 September, 1740, at Rougemont, in Alsace 3; d. 13 August, 1809), who, for the most part, left the government of his diocese to his vicar-general, Martin Wilhelm Fonck (b. 28 October, 1752, at Goch; d. 26 June, 1830, as Provost of Cologne Cathedral). After the death of Bishop Berdolet the diocese was governed by Le Camus, Vicar General of Meaux; after his death, in 1814, by the two vicars-general Fonck and Klinkenberg. The Bull of Pius VII, "De Salute Animarum," dated 16 July, 1821 which regulated church matters in Prussia anew, did away with the bishopric of Aachen, and transferred most of its territory to the archdiocese of Cologne; a collegiate chapter, consisting of a provost and six canons, taking the place of the bishopric in 1825. In 1815 Aachen became Prussian territory. The Congress of Aix-la-Chapelle sat there from 30 September to 11 November, 1818, and was attended by the sovereigns of Russia, Austria, and Prussia, and by plenipotentiaries from France and England, to determine the relations between France and the Powers. France obtained a reduction of the war indemnity and the early departure of the army of occupation, and joined the Holy Alliance; the other four Powers guaranteed the throne of France to the Bourbons, against any revolution that might occur. Aachen, under Prussian government, returned to prosperity, chiefly through the development of the coal mines in the neighborhood, which facilitated several extensive industries (such as the manufacture of linen, needles, machinery, glass, woolen, and half-woollen stuffs, etc.), but also in consequence of the large number of visitors to its hot springs.
Ecclesiastically, Aachen constitutes a deanery of the archdiocese of Cologne. It has a collegiate chapter, already mentioned, with a provost, six regular and four honorary, canons; 12 Catholic parishes, 46 Catholic churches and chapels; in 1906, there were 87 secular, and 24 regular, clergy, besides