The man behind the most famous symbol of France was not legally named Eiffel until he was nearly 50; for five decades he was Alexandre Gustave Bonickhausen. Born in Dijon in 1832, he grew up watching his mother turn a modest charcoal business into a lucrative coal distribution operation, and his uncle Jean-Baptiste, a chemist, filled his head with science. He graduated 13th in his class from the École Centrale in Paris in 1855 with a specialty in chemistry, not architecture. A family dispute sent him to work for a railway engineer, and by his late 20s he was building a 500 meter railway bridge over the Garonne in Bordeaux using compressed air caissons and hydraulic rams.

His own firm, founded in 1865, shipped prefabricated bridges as far as Cochinchina and Peru, left the iron exposed on a Budapest railway station, and threw a 160 meter arch over the Douro for the Maria Pia Bridge. He designed the flexible internal pylon of the Statue of Liberty and floated the Nice Observatory dome on magnesium chloride so one person could turn it by hand. The 300 meter tower for the 1889 World’s Fair began as a sketch by his engineers Maurice Koechlin and Émile Nouguier. Then came the Panama Canal: in 1893 he was convicted of misusing funds, later acquitted on appeal, and he left his own company. He spent his last decades in wind tunnels, won the Smithsonian’s Langley Medal in 1913, and died in 1923 at 91.

• How upside-down iron caissons let workers dig dry foundations at the bottom of the Garonne
• Why his math let him underbid rivals on the Maria Pia Bridge: he knew exactly how little iron he needed
• 18,000 pre-drilled parts, holes aligned to a tenth of a millimeter, and newspaper rumors that he had been locked in an asylum
• The Canal Company’s 1888 collapse and how his fame made him the most visible target for prosecutors
• Dropping instrumented surfaces from the tower, testing wing models for the Wright brothers and Louis Blériot, and showing that lift comes from a pressure difference