The name of the man who wrote the book How the Other Half Lives was Jacob Riis. His profession was journalist. He was a reporter for newspapers in New York City.
Jacob Riis was born in Denmark in 1849 and came to the United States when he was 21 years old. After a long time and many job changes, he ended up as a journalist. He became famous as one of the “muckrakers” who became such an important part of the Progressive Era. These were journalists and others who worked to expose negative conditions in US society of the time. Riis, of course, focused on the terrible conditions in which so many immigrants lived in American cities. He wanted to publicize the problems so that reforms could be undertaken that would alleviate the problems. This is why he took pictures of immigrant life in New York tenements, as seen in How the Other Half Lives.