fire in the Ohio Penitentiary in Columbus, United States kills 320 people. The Turkestan–Siberia Railway is completed. April 22 – The United Kingdom, Japan and the United States sign the London Naval Treaty to regulate submarine warfare and limit naval shipbuilding. May May 6 – The 7.1 Salmas earthquake shakes northwestern Iran and southeastern Turkey, with a maximum Mercalli intensity of IX (Violent); up to 3,000 people are killed. May 10 – The National Pan-Hellenic Council is founded in Washington, D.C. May 15 – Nurse Ellen Church becomes the world's first flight attendant, working on a Boeing Air Transport trimotor. May 16 – Rafael Leónidas Trujillo is elected president of the Dominican Republic. May 17 – French Prime Minister André Tardieu decides to withdraw the remaining French troops from the Rhineland (they depart by June 30). May 24 – Amy Johnson lands in Darwin, Australia, becoming the first woman to fly solo from England to Australia (she left on May 5 for the 11,000 mile flight). June June 7 – Carl Gustaf Ekman becomes Prime Minister of Sweden, for the second and final time. June 14 – The Bureau of Narcotics is established under the United States Department of the Treasury, replacing the Narcotics Division of the Prohibition Unit. June 17 – President Herbert Hoover signs the Smoot–Hawley Tariff Act into law, implementing protectionist trade policies in the United States. July July 4 – The dedication of George Washington's sculpted head is held at Mount Rushmore, South Dakota. July 5 – The Seventh Lambeth Conference of Anglican bishops opens. This conference approves the use of birth control in limited circumstances, a move away from the Christian views on contraception expressed by the Sixth Conference a decade earlier. July 7 The Lapua Movement marches in Helsinki, Finland. Building of the Boulder Dam (later known as the Hoover Dam) is started on the Colorado River, in the United States. July 11 – Australian cricketer Donald Bradman scores a world record 309 runs in one day, on his way to the highest individual Test innings of 334, during a Test match against England. July 13 – The first FIFA World Cup starts: Lucien Laurent scores the first goal, for France against Mexico. July 19 – Georges Simenon's detective character Inspector Jules Maigret makes his first appearance in print under Simenon's own name, when the novel Pietr-le-Letton (known in English as The Strange Case