Léon Lalanne

Léon Louis Lalanne, real surname Chrétien-Lalanne (3 July 1811 – 12 March 1892) was a French engineer and politician.

Lalanne was born in Paris on 3 July 1811, as Léon Louis Chrétien, the son of François Julien Léon Chrétien, a physician, and his wife Aurore Marie Damaris Langlois; his surname became Lalanne-Chrétien in 1820, Lalanne being the unmarried name of his father's first wife, and he dropped the Chrétien for practical use. He was the brother of the historian Ludovic Lalanne (1815–1898).

Lalanne studied at the Lycée Louis-le-Grand, where he was a classmate of Évariste Galois. From 1829 at the École Polytechnique, he went on to the École des ponts et chaussées in 1831. After that, he was a civil engineer, working mostly in northern France from 1832 to 1843. In 1837 he went on the group visit to Southern Russia organised by Anatoly Demidov. From 1839 he was working also with Jean-Claude-Républicain Arnoux, his future father-in-law, on the Ligne de Sceaux; he married in 1841.

During the Revolution of 1848, Lalanne was briefly made head of the Ateliers Nationaux (National Workshops). He undertook a severe rationalisation of the structure set up by Émile Thomas. Brought in during May, he had closed down the institutions of the Ateliers by the end of June. In the civil unrest that occurred simultaneously he commanded a battalion of the Garde Nationale in Paris. He was detained as a subversive on 29 June, but all charges were dropped on 5 August.

As a civil engineer, Lalanne became known for railway construction in Spain, Switzerland and Wallachia, where he was first engaged in 1852. He went to Bucharest in 1852, but encountered difficult local conditions. Russian operations against Ottoman possessions from July 1853, preceding the outbreak within months of the Crimean War, made his position untenable as French and British diplomats left.

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