Peak Map is a software tool that assists the user with matching unknown peaks from gamma spectroscopy measurements with corresponding decay signatures and generating nuclide libraries to be used in gamma spectroscopy analysis. The system uses nuclear data for the International Commission on Radiological Protection publication 107: Nuclear Decay Data for Dosimetric Calculations (ICRP-107) as a nuclear data reference however, the system is deigned in such a way other data references can be used in future releases. Peak matching is done by matching the energy of a peak to find nuclides with corresponding gamma line signatures and then provides a score. The score based on the difference in energy of the peak and line, the photon yield of the, and the half-life of the nuclide in relation to the time between the reference date and the measurement date. To further increase the confidence of the selection, the other signature lines of the parent, and of the daughters in equilibrium, are provided with a line match score that is determined by whether the lines that should be detected have matching peaks in the list. The signature lines and the matching nuclide information can then be written to a nuclide library file.