4G service is the latest in cellular technology.
The company said 4G service is ten times faster than the previous 3G service.
General Manager Nancy Garvey said this is a big step for the city.
"We rolled out 4G LTE in Kansas City last year and we've been expanding throughout the year, so it's really important because customers are doing so much with their devices," Garvey said.
AT&T also invited the mayor and the St. Joseph Metro Chamber of Commerce to attend the event.