Tretyakov Gallery was established in 1856 by Pavel Tretyakov.  He started to collect paintings in the beggining of 1850s. The collection went up and after some years Tretyakov decided to favor this gallery and his collection with the Muskovites. He asked them only not to enlarge his collection with other paintings and not to take money for visiting this museum. Unfortunately, nobody follows such requests, that's why nowadays you can see a supplemented collection of paintings after you've bought a ticket.