Louis I, Grand Duke of Hesse

Kronenthaler of Louis, Grand Duke of Hesse and by Rhine, 1825.

Louis was the son of Louis IX, Landgrave of Hesse-Darmstadt, and succeeded his father in 1790. He presided over a significant increase in territory for Hesse-Darmstadt during the imperial reorganizations of 1801-1803, most notably the Duchy of Westphalia, hitherto subject to the Archbishop of Cologne. Allied to Napoleon, Louis in 1806 was elevated to the title of a Grand Duke of Hesse and joined the Confederation of the Rhine, leading to the dissolution of the Empire. At the Congress of Vienna in 1814/15, Louis had to give up his Westphalian territories, but was compensated with the district of Rheinhessen, with his capital Mainz on the left bank of the Rhine. Because of this addition, he amended his title to Grand Duke of Hesse and by Rhine.

In 1844, a 33-meter column called Langer Ludwig (meaning Long Louis), was set up In his commemoration in the middle of the Luisenplatz, the largest square of Darmstadt.

In 1776, he became engaged to Sophie Dorothea of Württemberg, eldest daughter of Frederick II Eugene, Duke of Württemberg. The engagement was broken off so that Sophia Dorothea could marry Louis's recently widowed brother-in-law Tsarevich Paul Petrovich, son and heir of Catherine II "the Great", Empress of Russia. He received a monetary compensation when the engagement was broken.

On 19 February 1777, Louis married his first cousin, Princess Louise of Hesse-Darmstadt ( 15 February 1761 – 24 October 1829), a daughter of Prince George William of Hesse-Darmstadt. Together, they had eight children:

• Louis, later Grand Duke Louis II of Hesse (26 December 1777 – 16 June 1848). Married his double first cousin Wilhelmine of Baden and had issue.
• Louise (16 January 1779 – 18 April 1811). Married Louis of Anhalt-Köthen and had issue.
• George (31 August 1780 – 17 April 1856). Married, morganatically, Caroline Török de Szendrö and had issue.
• Frederick (14 May 1788 – 16 March 1867)
• Stillborn twin daughters (11 May 1789).
• Emil (3 September 1790 – 30 April 1856)
• Gustav (18 December 1791 – 30 January 1806)