Sprint now covers 67 markets with 4G LTE service. They jus added 9 new ones to their overall roster. Here's a list of the new ones,
  • Altoona, Pa.
  • Asheville, N.C.
  • Columbus, Ind.
  • Elkhart/Goshen, Ind.
  • Hammond, La.
  • La Crosse, Wis.
  • San Juan, Puerto Rico
  • Statesville, N.C.
  • Temple, Texas

Here's a copy of their press statement,

“With today’s announcement, Sprint is enabling even more customers to sample the power of 4G LTE on their smartphones, tablets and wireless hotspots.”

Bob Azzi, senior vice president-Network, Sprint

Sprint customers in 67 markets now are experiencing faster speeds for uploading photos, surfing the Web and streaming videos.

We are launching 4G LTE in nine new areas as part of our efforts to bring a better wireless experience to more customers every day as we build out an all-new 3G and 4G LTE network.

“The network team continues to build and test the new network across the country, including areas like San Francisco, Los Angeles and New York,” said Bob Azzi, senior vice president-Network, Sprint. “Customers report they are already finding a 4G LTE signal in these places, and we look forward to providing even more reliable access to the data they need with our official launches.”

Sprint 4G LTE is launching in:

Altoona, Pa., Asheville, N.C., Columbus, Ind., Elkhart/Goshen, Ind., Hammond, La., La Crosse, Wis., San Juan, Puerto Rico, Statesville, N.C., and Temple, Texas.

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Customers in 4G LTE service areas will be able to use their smartphones – such as Samsung Galaxy S® III, Samsung Galaxy Note® II or LG Optimus G™ – to share a picture of their favorite band performing at a local arena or to check the Web for basketball scores with greater speed.

Through April 11, with Switch to Sprint save $100 instantly on the Samsung Galaxy S II or the Galaxy S III[i]
Source: Sprint Community