Radio Astronomy in the U.S. went through two distinct phases, thepioneering phase before the Second World War, when Karl Jansky andGrote Reber were the only two radio astronomers in the world, and thepost-WWII era, when the subject blossomed throughout the world,especially in England and Australia, while U.S. radio astronomylanguished at a relatively low level, until its resurgence a decadelater. Here in Budapest we are celebrating the 70th anniversary ofJansky's discovery, and I shall start with a review of his work, andthe subsequent work of Grote Reber, who died, regrettably, in December2002. Two historical references will be cited frequently: Serendipitous Discoveries in Radio Astronomy (Kellermann & Sheets,eds. 1983, referred to as Paper 1) and the two historicalcollections edited by W.T. Sullivan, Classics in RadioAstronomy (1982, referred to as Paper 2) and The Early Yearsof Radio Astronomy (1984, Paper 3).