The invention of the atomic force microscope by Binnig, Quate and Gerber was a key development in nanoscience and inspired many other cantilever-based force detection modalities. One of the most important modalities is magnetic force microscopy, which has become a standard technique widely used for the study of magnetic materials and spintronic devices. I will describe some of the early efforts in magnetic force microscopy and its evolution toward ever increasing sensitivity. A key inspiration for our work came from John Sidles (Univ. of Washington) who suggested that force detection techniques might be applied to magnetic resonance detection and possibly achieve three-dimensional imaging of molecules. Motivated by this possibility, our group at IBM-Almaden pushed the sensitivity of cantilever-based force detection to the attonewton level, allowing the detection of a single electron spin and, later, nanoscale nuclear spin imaging. This talk will give a personal perspective of this research journey. Various innovations developed along the way will be highlighted, as well as some of the remaining challenges.  G. Binnig, C. F. Quate, and Ch. Gerber, "Atomic Force Microscope", Phys. Rev. Lett. 56, 930 (1986).  J. A. Sidles, "Folded Stern-Gerlach experiment as a means for detecting nuclear magnetic resonance in individual nuclei", Phys. Rev. Lett. 68, 1124 (1992).