In October 1990 CIPSCO Incorporated was formed as the holding company for Central Illinois Public Service Company, allowing creation of an investment subsidiary and laying the groundwork for investments in co-generation, independent power production and other initiatives.

Union Electric crews inspect and switch off transmission lines flooded during the summer of 1993.

CIPS signed a letter of intent with Union Electric Company to acquire new territory in eastern Illinois along the Missouri-Iowa-Illinois borders in January 1993, allowing 4,200 customers representing 20 megawatts of peak demand to join the CIPS system.

The 1990s also brought change and joined histories. In 1993, CIPS and Union Electric both battled a 500-year flood. Hardest hit in Union Electric territory was the St. Louis metropolitan area -- particularly those areas bisected by the swollen Missouri and Mississippi rivers. The flood forced 20,000 UE customers from their homes, inundated major substations, toppled transmission lines and eliminated transport of coal, forcing the utility to generate less to conserve fuel.

In 1994 Union Electric shared the industry's highest honor -- the Edison Award -- with Midwest Power Systems, Inc., of Des Moines, Iowa, for heroic efforts to provide electric service to customers in the face of the disastrous flood of 1993.

Union Electric receives the Edison Award for its work in the flood of 1993.

One year later, in 1995 Union Electric began a six-year incentive regulation program that allowed the company to bring more than $425 million in rate reductions and credits to its Missouri customers while sharing earnings above a certain return-on-equity threshold with shareholders. The year also marked the announcement of the proposed merger of CIPSCO Incorporated and Union Electric Company.

The Federal Regulatory Commission in 1996 issued new rules requiring electric utilities to open their transmission lines. The new rules created power marketing competition and eventually prompted Union Electric to create a profitable nonregulated power trading operation.

Transmission lines are used by more than one electric utility at a time. In 1996, the Federal Regulatory Commission issued new rules, requiring utilities to open their transmission lines to other power producers.

In Illinois, the world-class CIPS Pawnee Gas Training Center opened in May 1996. The Pawnee Customer Contact Center opened two months later at the same site, centralizing and consolidating customer service operations.

CIPS also announced in June 1996 that Newton Plant would switch to low-sulfur western coal and cease its scrubbing operations, yielding $100 million per year in fuel cost savings.

In December 1997 the merger of Union Electric and CIPS was completed, shortly after a law restructuring the electric utility industry in Illinois went into effect. The law phased in the right to choose providers, with large commercial and industrial customers getting choice by 1999 and all businesses and residential customers able to choose providers by May 2002. Other company and industry changes were on the way as well:

Newton Plant switches to low-sulfer western coal, ceasing its scrubbing operations.

In January 1998, Ameren Corporation created AmerenEnergy -- an energy trading affiliate that sells energy and a range of energy services targeted to customers in new markets.

And in November 1999 Archer Daniels Midland selected Ameren as its energy supplier and in August 2000 became a 300-megawatt Ameren customer. The international agricultural giant's Decatur, Ill.-facility is the largest single user of power in Illinois.