This dissertation explores how cities achieve fiscal sustainability—the financial capacity to consistently meet basic public service responsibilities regardless of economic conditions. Two research questions arise from the interplay between the local economy and fiscal sustainability. First, what management tools do cities use to achieve fiscal sustainability given that economic conditions are largely outside their control? Second, what explains the variation among cities in the financial management tools used to achieve fiscal sustainability? The financial management tools of interest in this study are revenue diversity and the size of the fund balance. It is conjectured that financial management tools interact with each other prompting the tools to function as policy substitutes for each other. Cities achieve fiscal sustainability by strategically choosing budget-balancing tools appropriate to their economic conditions. The study utilizes a cross-state comparison from 351 Massachusetts municipal governments using panel data from 2000 to 2009 and 993 New York municipal governments using panel data from 2001 to 2010. Using theories of fiscal sustainability and revenue diversification, several models are proposed that test the interactive effects of fund balance size and revenue diversity on fiscal sustainability. The results from the empirical analyses show that cities use various financial management tools to stabilize spending during economic downturns. Cities pursue strategies that help maintain fiscal sustainability. Furthermore, it is discovered that interaction of fund balance and revenue diversity on municipal expenditures is stronger as the level of revenue diversity decreases. This interaction has a large effect during periods of economic downturns as compared to periods of economic growth.