The E-1 Treaty Trader visa exists for citizens of countries that maintain treaties of commerce and navigation with the United States. In order to qualify for an E-1 visa the applicant must be coming to the U.S. to conduct trade between the U.S. and the treaty country.
The applicant's spouse and children under age 21 may apply for derivative E-1 visas. The spouse is eligible for work authorization, children are not. The duration of E visas is governed by the treaty, and by diplomatic reciprocity tables.
The E-1 Treaty Trader visa is used much less often than the E-2. The E-1 exists for a company that has substantial trade with the owner's home country. This trade can be goods, technology, or services.
Nationality - you must be a citizen of a treaty country. See the list here: treaty countries (eligible for E visas).
The trading firm you work for must have the nationality of the treaty country (must own at least 50%)
Trade must be substantial
More than 50% of the international trade must be between the U.S. and the treaty country
You must be an essential employee, employed in a supervisory or executive capacity, and must possess specialized skills essential to the firm.