A little unfortunate you limit yourself to "prints bigger than 24" on the wide side. Otherwise, there are plenty important galleries that show the work of many wonderful photographers, from the past to the present. To just name two galleries that I am very familiar with: Howard Greenberg Gallery and Tom Gitterman gallery. The first quite large, with many known photographers, the second a smaller gallery but run by someone who makes no distinction between a collector or a student coming in. He gives time and his wonderful knowledge to anyone interested.