The "Journal für die Reine und Angewandte Mathematik" or "Crelle's Journal" is the oldest mathematical journal in existence. To celebrate its 200th anniversary, this book republishes eight influential articles, one for each 25-year period. Each paper is followed by an extended commentary discussing its background and content, and reassessing its current significance. The articles reproduced here, some of them for the first time in English, cover a wide range of topics: algebra, analysis, algebraic geometry, dynamics, and number theory. A historical introduction situates Crelle's Journal within the mathematical research journals over time.