I didn't know what this ment until I saw a 1x at the top of my new cell phone, the Motorola V60s.
Aparently, 1x is short for 1xRTT, and is actually an acronym. 1x means single carrier, RTT means radio transmission technology. This was made in the United States and is used as a 3G wireless technology that is based on CDMA. The cool thing about 1xRTT is the speeds, almost 86kbit/s, although I have heard the actual speeds are more like 40-60kbit/s. 1xRTT is actually a packet based wireless network, unlike most other cellular data networks that are "dialup" networks.
At this time, I believe that Verizon Wireless, AT&T, Cingular, and Sprint have already setup 1xRTT networks or are in the late planning stages.
I should note that my provider is Verizon Wireless, and I am sure that they offer 1xRTT.