Local reports in the Commonwealth of the Northern Marianas say last week's so-called "unity march" may be the largest public gathering in CNMI history.
Estimates of crowd numbers vary from 3,000 to 15,000.
The Marianas Variety newspaper says the march, which was organised by guest worker groups and local residents, urged the repeal of the CNMI's latest labour law and the extension of federal immigration laws to the islands.
The recently-passed Northern Marianas law requires foreign workers to leave the islands for six months before returning for new contracts.
The marchers also supported legislation pending in the U.S. Congress that would federalise control of the Northern Marianas' immigration and labour departments.