From ArborWiki

Annexation is the process of moving parcels from one jurisdiction to another. In some cases, entire cities are annexed; in others, entire neighborhoods; or, it might be parcel by parcel.

The City of Ann Arbor's municipal boundary, which is mostly circumscribed by the freeway ring, has a series of township islands in it.

[edit] Sources

• This 2007 discussion on Arbor Update describes the situation then.
• The city of East Ann Arbor was annexed into the city of Ann Arbor in the late 1950s.
• Annexation of Township Parcels, City of Ann Arbor, File # 11-0750
• Potential Annexations, City of Ann Arbor. PDFs of maps showing parcel by parcel which are possible for city annexation.