The E-1 Treaty Trader category dates back to the time before alliances like the European Union or NAFTA existed and countries entered bilateral treaties so their citizens could trade across borders. In some countries, the E visa has already been in existence for more than 100 years.
Of course, the eligibility criteria for this category have been changed and adjusted over the course of the past decades.
Qualified employees of companies who are engaged in substantial trade with the United States may qualify for this category. A self-employed individual may qualify for this category the same way an employee of a medium-sized enterprise or a multinational company does. While the L-1 visa requires an office outside the U.S., the E visa is available without that. However, the company must have an office in the U.S.
PLEASE NOTE: Since a simplified application process is available for E visa applications, it is advisable to always consider this visa as an alternative to other work visas. Compared to other work visas, the application for this particular one saves a lot of time and money even in the short run, especially for companies who frequently need to send employees abroad.