In 1915 he produced "The Rothschild List", a schedule of the best 284 wildlife sites in the country, some of which were purchased as nature reserves. As well as a Lieutenant of the City of London, Rothschild became a JP for the county of Northamptonshire in 1902. He served as High Sheriff of Northamptonshire for 1905. In 1907, Rothschild married Rózsika Edle von Wertheimstein (1870–1940), a descendant of an old Austrian-Jewish family that was ennobled long before the Rothschilds. She was born in 1870 at Nagyvárad, Hungary (now the Romanian city of Oradea), the daughter of a retired army officer, Baron Alfred Edler von Wertheimstein. Alfred's sister Charlotte was married to . Rózsika was one of seven children. She was a very beautiful woman with dark brown eyes. Each eye had a purple ring to it, and they could flicker strangely. She was also a voracious reader. Every day she would read a Hungarian newspaper, a German newspaper, an English newspaper, and quite often a French one, too. She read all the political articles in these papers. Rózsika had even been a champion lawn tennis player in Hungary. After their marriage on 6 February 1907, they lived at Tring and in London. Rothschild, who worked in the family’s banking business, was a dedicated naturalist in his spare time: the young couple had met on a butterfly-collecting trip in the Carpathian Mountains. In the evening, they might go together to a concert or a dinner party, but he really preferred to sort out his butterflies. Together, they had four children:   Suffering from encephalitis, in 1923 Rothschild committed suicide. His suicide, when he was 46 years old, was a severe shock to his wife and four children. Rózsika died on 30 June 1940.