Public transportation accessibility has a remarkable impact on the well-being of marginalized communities, especially those situated in underserved regions. However, disproportionate geographical distribution of transit services often results in disparities in accessing public transportation. Therefore, it is imperative to pinpoint areas where there exists a disparity between transit demand and supply, commonly referred to as "transit deserts," particularly concerning disadvantaged population groups. This study investigates the spatial accessibility of public transit with a specific focus on minority communities in northeastern Illinois, U.S. To accomplish this, we have introduced a Needs Gap index, which characterizes the incongruity between transit demand and supply for different demographic groups. Our analysis is based on data from the 2020 American Community Survey, aggregated at the census tract level. The outcomes of our study provide valuable insights into the geographic pattern of transit deserts, considering both the overall population and specific minority groups, encompassing various demographics such as race, age, and income. Notably, our preliminary analysis underscores that the Hispanic community experiences the most pronounced underservice compared to other racial groups. Furthermore, this study underscores the significance of concentrating on particular demographic cohorts when identifying transit deserts, instead of solely focusing on the entire population. By doing so, we aspire to provide a more comprehensive understanding of the disparities related to transit deserts in the study area. Ultimately, our findings can be instrumental in aiding policymakers and transit authorities in formulating strategies to enhance transit accessibility and promote equity within the public transportation system throughout the region.