Who published an expose of slums and other urban problems titled how the other half lives in 1890?

The Dutch author and photojournalist Jacob Riis published "How the Other Half Lives," describing New York tenement slums in 1890. This exposed the squalid conditions that (mainly poor, ethnic) New Yorkers lived in during the 1880s and led to reforms in the housing code to better allow tenants to be able to survive in their dwellings.

The mountains on the east would be taller