Fallout radionuclides (FRNs) such as ¹³⁷Cs and ^239+240Pu are considered to be critical tools in various environmental research. Here, we compiled reference soil data on these FRNs from the literature to build a comprehensive database. Using this database, we determined the distribution and sources of ¹³⁷Cs and ^239+240Pu. We also demonstrated how the database can be used to identify the environmental factors that influence their distribution using a machine learning algorithm.