U. S. Equity Trading Industry has evolved quickly over the last decade. The U.S. equity market became an open architecture in which entrants with innovative technology can compete effectively. Several regulatory changes and technological innovations have enabled profound changes in market structure. These changes, along with improving high-speed technology, have acted as a catalyst, giving rise to a new approach to trading, named High Frequency Trading, hereafter referred as HFT. HFT Firms emerged and took over in large extent the market making business in providing liquidity. Although HFT has been growing massively, over the past four years, HFT firms have been far less profitable, since more firms entered the industry eroding the margins. Within this context, therefore, this thesis sought to provide a brief review of HFT business, followed by the analysis of its industry boundaries and the characteristics of the HFT environment. To this end, the thesis conducted an extensive literature review of previous research, qualitative public documents, such as, newspapers, meeting minutes and official reports. The thesis employed a series of frameworks, Entry Barriers and Mobility Barriers (Porter, 1980); Models of Industry Evolution (McGahan, 2004); Information-Intensive Industry Structure (Sampler, 1998), to analyze the boundaries of the HFT industry. Additionally, it employed Models of Industry Evolution (McGahan, 2004) and PESTEL (JOHNSON, SCHOLES, and WHITTINGTON, 2011) frameworks to analyze the industry and the environment surrounding HFT business. The analysis concluded that the firms employing HFT to compete in the Securities Trading industry compose an independent industry.