Binary silicophosphate glasses containing between 7 and 35 mol% P2O5 were made by conventional melt quenching techniques and characterized by 29Si and 31P NMR spectroscopy. 31P and 29Si NMR data show that, as the P2O5 content is raised in these glasses, the network connectivity is decreased by a dilution of the silicate network with less polymerized Q3 phosphate groups. In addition to such changes in the network structure, 29Si NMR spectra for the most P2O5-rich glasses reveal the presence of silicon atoms with 5- and 6-fold coordination. These species increase in concentration with increasing P2O5 above approximately 30 mol% P2O5. Self-nucleating SiP2O7 glass-ceramics can be formed from the binary silicophosphate glasses with >25mol% P2O5. 29Si and 31P NMR results were used to monitor the crystallization of SiP2O7 by providing details on amount of crystallinity, relative grain sizes and even composition of the residual glassy matrix. Stabilization of octahedral Si as well as the onset of phase separation correlates with propensity for crystallization of SiP2O7 during subsequent heat treatment.