The Northridge earthquake of January 17, 1994, caused structural damage to a number of welded steel moment-frame (WSMF) buildings of different heights and ages. The structural damage indicated that WSMF connections were susceptible to fracture when subjected to strong ground shaking. This paper describes the geometry and fracture behavior of pre-Northridge and of unreinforced post-Northridge WSMF connections. The origin, size, and geometry of the fracture initiating defects are discussed, as are the stresses and strains, and the materials at the fracture initiation sites. The factors needed for an accurate fracture mechanics analysis of pre-Northridge WSMF connections are discussed. Analysis of the crack propagation paths and the different types of fractures in the pre-Northridge and in the post-Northridge WSMF connections are included.