The Cretaceous-Tertiary (KT) mass extinction is primarily known for the demise of the dinosaurs, the Chicxulub impact and the frequently rancorous 30 years old controversy over the cause of this mass extinction. Since 1980 the impact hypothesis has steadily gained support that culminated in 1990 with the discovery of the Chicxulub crater on Yucatan as the KT impact site and ‘smoking gun’ that proved this hypothesis. In a perverse twist of fate this discovery also began the decline of this hypothesis because for the first time it could be tested directly based on the impact crater and impact ejecta in sediments throughout the Caribbean, Central and North America. Two decades of multi-disciplinary studies amassed a database with a sum total that overwhelmingly reveals the Chicxulub impact as predating the KT mass extinction in the impact crater cores, in sections throughout NE Mexico and in Brazos River sections of Texas. This chapter recounts the highlights of the KT controversy, the discovery of facts inconsistent with the impact hypothesis and the resurgence of the Deccan volcanism hypothesis as the most likely cause for the mass extinction.  PDF