Walter Rudin died on May 20, 2010 at the age of 89 after a long illness.
Many of us learned mathematics from some of his books or papers. His being at the Univ. of Wisconsin was one of the main reasons I came here. His book on real and complex analysis was written for a course needed here. It provided a book which made it possible to teach enough real and complex variables so students could move to more specialized courses in analysis after a year of graduate study rather than the two years needed previously when there were year courses in real variables and complex variables. Informally among graduate students, his books were called the blue Rudin, the green Rudin, the yellow Rudin, etc. The fact that he wrote them seemed to many to be more important than using the title of the book.
To learn more about W.R., see also here.