This chapter addresses assessment (testing) with an emphasis on the 100-year period since the American Education Research Association was formed. The authors start with definitions and explanations of contemporary tests. They then look backward into the 19th century to significant work by Horace Mann and Herbert Spencer, who engendered two parallel purposes for assessment: evaluating effects of education and identifying individual differences. The authors consider the interplay of these orientations over the years. After discussing policy impacts on assessment, they discuss the evolution of the concept of validity as it relates to changing rationales for testing. To enrich the reader's comprehension, the authors also discuss perspectives on innovation in technology and in quantitative analysis. They conclude with questions that summarize current concerns with assessment. Finally, they consider future prospects for assessment. They foresee the continued convergence of assessment purposes, innovative learning technology, and new psychometric challenges.