AmerenUE is cutting ties with its past, shedding the most visible link to the 108 year-old Union Electric Co.

Missouri's largest utility will be instead known as Ameren Missouri beginning Oct. 1.

Ameren customers in Missouri will begin getting notice of the name change in mailings. The change coincides with a merging of the company's three Illinois utilities — AmerenIP, CIPS and Cilco — which will be known as Ameren Illinois beginning Oct. 1.

The name change was meant to ease confusion among customers and make it easier to communicate, Thomas R. Voss, CEO of the holding company for the utilities, said in a statement.

Several of Ameren's key markets, including the St. Louis area, include customers in both states. Until a few years ago, there were AmerenUE customers on both sides of the river. That led to confusion over differing rates, services and regulations, spokesman Mike Cleary said.

"By making the state part of the name of the company, it should help clarify what company is doing what," Cleary said.

Ameren is also redesigning bills for Missouri customers to make them clearer and easier to understand. But the utility won't spend money to advertise the name change, and rebranding will be done over time to avoid "unnecessary costs."

Trucks, uniforms and building signs will be updated over time as worn-out materials and equipment is replaced, Cleary said.

"You're going to be seeing the AmerenUE and other logos for some time," he said.

The origin of the Union Electric name dates back to 1902 when Union Co. was formed with 2,000 customers and 6 megawatts of generation capacity. The utility helped illuminate the 1904 World's Fair in St. Louis.

The 1998 merger of Union Electric and Cipsco Inc. created Ameren Corp. The Missouri utility was renamed AmerenUE.

Today, the utility has 1.2 million electricity and natural gas customers across much of eastern Missouri. While the Ameren name has been in place for more than a decade, it is still known to many longtime St. Louis-area residents as Union Electric, or simply UE.

"All of these (Ameren) companies have very proud traditions. But today, people more identify with the Ameren name," Cleary said.

"They want good service and being able to effectively communicate is part of providing good service."