How did jacob riis call attention to slum conditions? be specific

He called attention to slum conditions through taking photos and documenting poverty in New York City. This made him a famous campaigner against slum housing. He also led a team of photographers who were with the police to inspect a slum area. In there, a picture was taken and used as a document of urban poverty. One of his known photos was called "5 Cents a Spot" which displays a room filled with people staying together to sleep during the night. Through public slideshows and in his book entitled How the Other Half Lives, he used a lot of the photos he took and his descriptions to hit the conscience of rich Americans. 

Word of mouth.