Formal mapping surveys of Ontario's soil landscapes began in 1914. Ontario soil scientists have included soil organic matter and other soil carbon information in soil survey reports, research study reports, journal articles, academic theses and field sampling analysis reports over the century of soil knowledge development for the province that followed. To date, no systematic province-wide maps of soil carbon status have been developed and published. Academic scientific inquiries and agricultural soil management programs have focused on various aspects of soil degradation, cropping system management for soil health enhancement and carbon sequestration in Ontario's soils. And yet, none of these studies have considered the actual shelf-life (and hence relevance to present-day conditions) of this reported soil carbon information for specific geographic locations. Furthermore, despite a legacy of studies of the short-range variability of soil properties (including soil carbon) across agricultural soil landscapes, Ontario's soil database does not reflect this in the soil carbon information provided for named soil series. This century of systematic soil landscape investigations in this province has led to a highly variable information resource on this important aspect of soil fertility and global climate change knowledge development. The relevance to current conditions of Ontario's legacy soil carbon information is challenged in this study. Results from several case studies are presented. Within-field soil carbon levels were assessed at locations mapped as specific soil series. Soil carbon levels were evaluated across broader landscapes for particular soil series. They were also assessed through time at the same location. These results differ enough from the corresponding legacy soil database information to conclude that these older data do not reflect current soil carbon levels meaningfully for Ontario's agricultural soil landscapes. A systematic renewal approach for Ontario's soil carbon database is being developed.