President Donald J. Trump underscored repairing the nation’s aging infrastructure as a national priority both throughout the campaign and in his inauguration address. Senate Democrats last week also unveiled their own $1 trillion plan. But how did the country’s infrastructure fall into a state of such disrepair? What are the greatest challenges facing an infrastructure boom? And how can engineering foster innovation and the development of new technology to address this national priority? We asked Jerome Hajjar, CDM Smith Professor and chair of the Department of Civil and Environmental Engineering.