AMEREN CORP

Overview

Ameren Corporation is a St. Louis-based utility holding company whose businesses provide electricity and natural gas in Missouri and Illinois. Ameren Missouri generates, transmits and distributes electricity and distributes natural gas; Ameren Illinois distributes electricity and natural gas. The company also operates electric transmission businesses. Its stated mission is “to power the quality of life.” [1][2]

Ameren serves approximately 2.5 million electric customers and more than 900,000 natural-gas customers. In 2025, it reported $8.8 billion in operating revenue and employed 8,913 people at year-end.[3][1] [4]+8

Products & services

Ameren’s principal services are electricity and natural gas. Ameren Missouri generates, transmits and distributes electricity and distributes natural gas; Ameren Illinois distributes electricity and natural gas and operates electric transmission facilities. Its gas utilities purchase gas and arrange pipeline transportation and storage to serve customers. In Illinois, customers can choose an alternative electric supplier while Ameren Illinois continues to provide distribution service.[10]+2

The electricity supplied by Ameren Missouri comes from a mix of generation technologies. At year-end 2024, its listed owned generating capability included 3,344 MW of coal, 1,194 MW of nuclear, 698.8 MW of wind and 515.3 MW of solar capacity.[13] Ameren also offers customer programs including energy efficiency and demand response.[14][15] In 2024, electricity accounted for $6.54 billion, or approximately 86%, of Ameren’s $7.62 billion in consolidated revenue; natural gas accounted for $1.08 billion, or approximately 14%.[16] [10]+11

Geographic presence

Ameren’s utility operations are concentrated in Missouri and Illinois. Ameren Missouri serves central and eastern Missouri, including the Greater St. Louis area, while Ameren Illinois serves central and southern Illinois. The company also operates electric transmission assets through Ameren Illinois and Ameren Transmission Company of Illinois; one transmission project extends from Missouri to Indiana.[10]+3

In 2024, Ameren Missouri recorded $3.96 billion in external revenue, or about 52% of Ameren’s $7.62 billion total. Ameren Illinois’s electric-distribution and natural-gas segments recorded a combined $3.03 billion, or about 40%. Ameren Transmission recorded $637 million, or about 8%; these are business-segment figures rather than a complete breakdown by customer location.[20] Ameren Corporation’s principal office is in St. Louis, Missouri, and Ameren Illinois’s principal office is in Collinsville, Illinois.[21][22] [10]+10

Business segments

Ameren reports four business segments. Ameren Missouri includes its Missouri electric generation, transmission and distribution operations, as well as natural gas distribution. Ameren Illinois Electric Distribution and Ameren Illinois Natural Gas cover those respective utility businesses in Illinois. Ameren Transmission primarily combines the electric transmission businesses of Ameren Illinois and ATXI.[23]

Based on 2025 revenue from external customers, Ameren Missouri contributed approximately 54% of Ameren’s $8.8 billion total, Ameren Illinois Electric Distribution 27%, Ameren Illinois Natural Gas 11%, and Ameren Transmission 8%. These percentages exclude sales between segments. Ameren also reports an “Other” category, primarily comprising parent-company activities and Ameren Services, rather than a fifth operating segment.[23] [24][23]

Company history

Ameren Corporation was formed in 1997 through the merger of Union Electric Company and CIPSCO Inc., the parent of Central Illinois Public Service Company. Its roots extend to the Union Company, organized in St. Louis in 1902 as a predecessor of Union Electric.[25][26]

Ameren expanded its Illinois utility business by acquiring Illinois Power from Dynegy in 2004. In 2010, it combined three Illinois utilities—AmerenCIPS, AmerenCILCO and AmerenIP—into Ameren Illinois Company. Ameren then sold its merchant-generation business in 2013, marking a shift toward regulated utility and transmission operations.[27]+2 [30]+6

Sources

• www.sec.gov[1]
• www.ameren.com[2]
• www.ameren.com[3]
• AMEREN CORP — Full financial report (2025 Y)
  7 citations

  [4][5][6][7][8][9][24]
• AMEREN CORP — Full financial report (2024 Y)
  12 citations

  [10][11][12][13][14][15][16][17][18][20][21][22]
• www.ameren.com[19]
• www.sec.gov[23]
• www.sec.gov[25]
• dynamic.stlouis-mo.gov[26]
• ameren.mediaroom.com[27]
• ameren.mediaroom.com[28]
• ameren.mediaroom.com[29]
• AMEREN CORP — Full financial report (2016 Y)[30][31]