A growing number of Americans are getting rid of their landline phones, and Seattle is in the top 10 list of cities where this trend is happening the fastest.

Detroit has the highest rate of "wireless substitution" among the 20 largest cities in the U.S., according to Telephia, with 19 percent of its households now wireless-only. Minneapolis-St. Paul was second with 15.2 percent. They were followed by Tampa, Atlanta, Washington, D.C., and Phoenix.

Seattle ranked seventh, with 13 percent of households going wireless. San Francisco, traditionally an early-adopter city, didn't make the top 10, and Telephia researchers guessed this might be because of the low mobile network quality in the area.

The Telephia study doesn't include people who have dropped their landline phones in favor of digital voice -- a service that has been readily adopted by Washington residents, according to Comcast.