Maygene Daniels, chief of Gallery Archives, National Gallery of Art, and Dorothy and Herbert Vogel, collectors. Dorothy and Herbert Vogel have amassed one of the greatest collections of minimal, conceptual, and post-minimal art in the world, acquiring works by some of the most important contemporary artists of our time. Daniels spoke with the Vogels about the 231 artist postcards in their collection—the personalized cards and other items that artists mailed to them, often with drawings, sketches, as well as personal messages.