An introduction to measure theory and Lebesgue integration rooted in the historical questions that led to its development.

1. Introduction; 2. The Riemann integral; 3. Explorations of R; 4. Nowhere dense sets and the problem with the fundamental theorem of calculus; 5. The development of measure theory; 6. The Lebesgue integral; 7. The fundamental theorem of calculus; 8. Fourier series; 9. Epilogue: A. Other directions; B. Hints to selected exercises.