This chapter begins with an account of the successful thwarting of Najibullah Zazi's plot to bomb the New York City subway system in 2009, which had been timed to coincide with the 8th anniversary of 9/11 to examine the effectiveness of America's domestic counterterrorism program since 9/11. It examines five high-profile terrorist attacks which were perpetrated, respectively those by Nidal Hasan, Faisal Shahzad, the Tsarnaev brothers, Syed Rizwan Farook and Tashfeen Malik, and Omar Mateen. In considering both thwarted and actual terrorist attacks, the chapter sheds light on the operation of counterterrorism in the United States in the post-9/11 era, how the nature of the threat has evolved and the challenges which face effective counterterrorism efforts. The United States faced threats from new prototypical home-grown terrorists: legal U. S. residents who are radicalized, motivated, and capable of executing terrorist attacks.