The Metropolitan Museum, in New York, has a amazing collection of various types of art from around the world. The important point is that photography is viewed as just another type of art, like sculpture, painting or Japanese woodblock prints. They have a large Walker Evans and Henri Cartier-Bresson art collection amongst others. Three whole galleries are dedicated just to photography.
As many people take photographs, it is harder to think of photographs as art, compared to a less common activity like woodblock printing. After all, a picture can be taken with just a click of a button.This overlooks the years that a artist needs to develop there own personal style and master there chosen medium. What is harder to understand is the need for an artistic vision. If you lack a artistic vision, then you can be a painter or photographer but not a artist. While not everyone with a camera is Ansel Adams, not every one with oil paints is Pablo Picasso.