This paper explores patterns of declining sense of community found in many modern-day neighborhoods and maintains that this phenomenon presents a level of vulnerability to our society that has been overlooked. It investigates this by examining four modern environments within the U.S.: two primarily low-income, immigrant communities in or near the Tempe area, and two middle-income class communities in downtown Mesa and on the South Texas border, respectively. It uses a multi-methods approach to understand how sense of community could manifest itself at varying levels depending on the type of community establishedamong different types of communities. The locations studied were fundamentally different in nature, and, therefore, could not be subject to comparative analysis. However, the study gives evidence of weaker sense of community and general relational connection among moderate to upper-class environments. Literature review utilized in the two low-income immigrant neighborhoods revealed that residents experience high sense of community, as well as high satisfaction with their environments. Qualitative analyses consisting of interviews approached through an assets-based community development perspective, as well as forms of coding employed in the South Texas neighborhood, revealed that the two middle to upper-income communities experience low to moderate sense of community, and corresponding satisfaction with their environments. This paper suggests that trends of decreasing sense of community, such as these, create unnoticed vulnerabilities for our modern environments that present disadvantages for sustainable development. It also suggests that we can learn from the former two communities, and proposes that strong communities are critical for our society on many levels, as well as advantageous for the future of sustainable development.