"Massachusetts - The Bay State" was designated the official state tartan of Massachusetts in 2002.

Illustration of classic Scot in kilt from Scottish Tartans Authority

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:

Tartans of Scotland
Scottish Tartans Museum; History

Links:

Cultural Symbols - 50 states