The State of Rhode Island was created as a state tartan by the St. Andrews Society of Rhode Island Inc. Officially recognized as the state tartan in 2000. Registered with the Scottish Tartans World Register as: Rhode Island, The State of Rhode Island.

Tartan refers to fabric woven into plaid patterns representing clans (families) or regions in Scotland.

In old Scotland, the tartan was used for clothing and as a banner or flag. Because a family or community worked the cloth together, their clothing was made of the same patterns, and so a person could be recognized by the Tartan plaid that he wore. Tartans can also be designed as a symbol commemorating a special event or person.

Source:

The Ocean State - History and Facts - Know Rhode Island: RI SOS

Links:

Cultural Symbols - 50 states