Number Portability Resource Center

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The map below shows the top 100 MSAs. These are areas where the FCC has mandated that number portability take effect November 24, 2003. For the remaining areas, the deadline in most cases is May 24, 2004.

For more detail, the FCC has a document that lists counties included in each MSA:

Top 100 MSAs by County
(PDF file - download Adobe PDF Reader here)

Although referred to as the "Top 100" MSAs, there are actually 102 areas. This is because between deadline delays, the 2000 census was released. Population shifts caused the top 100 list to change, so the FCC decided to include all MSAs that were in the top 100 in either the 1990 OR 2000 census.