- 1922 - Louis Desloge Sr. founds Watlow in St. Louis, Missouri to manufacture electric heating elements for the shoe industry. The company name Watlow is selected referring to "low-watt" heaters to replace steam heat. Watlow produced its first heaters in a rented corner space on the second floor of a machine shop.
- 1923 - Watlow pioneers the use of electric heat in brick presses with strip heaters and standard cartridge heaters, replacing the more costly steam process.
- 1924 - Watlow builds its first factory. The company introduces a line of consumer products, including electric irons and heating pads, under the name of Queen Quality.
- 1925 - Watlow improves the process of shaping the popular harvest hat by replacing gas heat - both hard to control and confine - with special electric heating units designed to fit the shape of the dies.
- 1931 - Watlow introduces electric immersion heaters replacing cumbersome steam pipes and fire-hazardous gas.
- 1945 - Watlow begins selling products outside the United States.
- 1948 - George Desloge, Louis's son, joins Watlow. George has a degree in aeronautical engineering.
- 1950 - George Desloge invents the narrow band cylindrical heater with its patented clamping strap for use in plastics processing.
- 1951 - Watlow expands into a larger manufacturing facility, which is more than 15,000 square feet.
- 1954 - George Desloge invents, and later patents, the FIREROD® cartridge heater, improving heat transfer efficiency in shoe manufacturing.
- 1958 - Watlow opens a facility in California and begins manufacturing silicone rubber heaters to service the aerospace industry. Watlow's FIREROD cartridge heater is patented.
- 1961 - Watlow builds a new 30,000 square foot facility on a 28-acre tract in St. Louis County, Missouri.
- 1963 - Louis Desloge Jr., Louis's son, joins Watlow and proceeds to build an international network of direct sales engineers and distributors.
- 1965 - George Desloge becomes president and Louis Desloge Jr. vice president of Watlow.
- 1967 - Watlow designs and manufactures the first high watt density cartridge pressurized heater for use in nuclear power plants.
- 1969 - Watlow expands its headquarters and St. Louis, Missouri, manufacturing location to 95,000 square feet.
- 1970 - Watlow's radiant heater line, RAYMAX®, is introduced.
- 1972 - Watlow opens a manufacturing facility in Hannibal, Missouri, to produce tubular heaters.
- 1973 - Watlow opens its first manufacturing facility outside of the U.S., in Germany, to produce metric diameter cartridge heaters.
- 1974 - Watlow introduces its thermocouple product line for the plastics industry.
- 1976 - Watlow purchases Waynco, Inc. of Winona, Minnesota, a manufacturer of electronic controllers. Watlow purchases Scaico Controls, manufacturer of cartridge heater thermostats.
- 1977 - Watlow purchases Aten Limited and begins producing ceramic fiber heaters.
- 1978 - Watlow acquires Magne-Cast, an aluminum mold foundry in Batavia, Illinois. Watlow is able to offer complete in-house cast-in aluminum heater design and manufacturing.
- 1979 - Watlow opens a new facility in Columbia, Missouri, to manufacture flexible and ceramic fiber heaters. Watlow begins manufacturing metric FIREROD cartridge heaters in Weihner, West Germany.
- 1981 - Watlow purchases Adlake's mercury displacement relay division, which adds power switching ability. Watlow expands its St. Louis, Missouri, manufacturing facility to over 185,000 square feet.
- 1982 - The patented Lead Adapter (LA) manufacturing process allows same-day shipment on more than 150,000 configurations of stock FIREROD cartridge heaters and lead combinations.
- 1983 - Watlow begins Pacific Heater Company in Pacific, Missouri, a manufacturer of cartridge heaters. Watlow introduces its high performance mineral insulated band and strip heater product line.
- 1984 - Watlow doubles the size of its Winona, Minnesota, facility.
- 1985 - Watlow acquires the Claud S. Gordon Company of Richmond, Illinois (founded 1914), the nation's leading manufacturer of temperature measurement devices. Watlow Gordon introduces the multipoint temperature sensor.
- 1986 - Watlow purchases IR-ONICS in Providence, Rhode Island, adding infrared temperature measurement capabilities. Watlow establishes a sales office in Milan, Italy. Watlow produces its first microprocessor-based temperature controller.
- 1987 - Watlow opens a new sales office in Nottingham, England. Watlow expands plant in Kronau, West Germany.
- 1988 - Watlow opens a new sales office in France. Watlow introduces the patented FIREBAR® flat tubular heater improving frying productivity in restaurant fryers. Watlow opens a new 170,000 square foot facility in Hannibal, Missouri, for manufacturing tubular heaters and assemblies.
- 1989 - Watlow purchases Loyola of Orange, California, an original developer of silicone controlled rectifier (SCR) control technology. Watlow purchases its largest British distributor and establishes manufacturing capabilities in Great Britain. A new sales office is established in Kaohsuing, Taiwan. Watlow moves its aluminum casting operation into a larger facility. A new infrared temperature sensors plant is opens in Decorah, Iowa.
- 1990 - Watlow opens a new facility in Troy, Missouri, dedicated to process system design and fabrication. Watlow opens a new sales office in Seoul, South Korea. Watlow introduces the SERIES 945, a microprocessor-based controller.
- 1991 - Gary Neal becomes president of Watlow. George Desloge becomes chairman of the board and Louis Desloge Jr. becomes vice chairman. Watlow acquires AOV Industries of Anaheim, California, and begins manufacturing high temperature MULTICELL™ heaters. Watlow opens a sales office and manufacturing facility in Singapore. Watlow doubles the size of its Columbia, Missouri, plant.
- 1992 - Watlow launches the new SERIES 92 limit/temperature controller and the SERIES 733 menu-driven cooking computer for the foodservice industry.
- 1993 - Watlow introduces the SERIES 988 process controller and the new DIN-A-MITE® power controller. The FIREROD MI lead option for high temperature and contamination resistance is patented. Watlow's new NSF-approved RTD meat piercing probe is rated up to 500°F (260°C).
- 1994 - Watlow dedicates a new facility to research and development in Fenton, Missouri. Watlow opens a sales office in Querétaro, Mexico. Watlow's launches the new XACTEMP® surface probe and the new SERIES 935 controller. Watlow's facility in Batavia, IL becomes ISO:9001 certified. The compact, low cost IR Junior infrared temperature sensor is introduced.
- 1995 - Watlow becomes a majority investor in Anafaze of Watsonville, California, a designer and manufacturer of multi-loop controllers and PC-based control operating software. Watlow Shanghai begins as a joint venture to support mainland China. Watlow begins Alliance Heaters Company in Montgomery City, Missouri, to manufacture higher volume tubular heaters and assemblies.
- 1996 - MINICHEF™ 2000, a foodservice industry controller, and the new MICRODIN™ DIN rail mount controller are introduced. Watlow's de Mexico facility begins manufacturing FIREROD cartridge heaters.
- 1997 - Watlow celebrates its 75th anniversary. Watlow topped the preferred supplier list for multi-loop and single-loop analog temperature controllers in North America according to The Worldwide Market for Industrial Temperature Controllers, published by Venture Development Corporation. Watlow introduces pump line heaters for semiconductor processing. Watlow opens a new sales office in Japan.
- 1998 - Watlow introduces FREEFLEX® miniature heated tubing and the PPC-2000, a programmable process controller. Watlow also introduces thick film heating technology on several substrates. Watlow acquires Energy Converters, Inc. (Encon), Dallas, Pennsylvania and Watlow Polymer Technologies, Inc. is formed.
- 1999 - Peter T. Desloge becomes chairman of the board and George B. Desloge becomes co-chairman of the Board. Watlow introduces the MULTICOIL™ heater, the first tubular heater to combine multiple resistance coils and thermocouples with three-phase capability. Thick film technology is expanded to include in-line quartz tubing for aggressive chemical heating. Watlow introduces a high-purity aluminum pedestal heater for the semiconductor industry. Watlow opens a new sales office in Australia.
- 2000 - Watlow Polymer Technologies introduces its patented THERMOPOLYMER® heaters to provide unique heated parts. Watlow is awarded winner of the Mississippi Valley Family Business of the Year Award, in the large Missouri business category by Southern Illinois University Edwardsville. Watlow expands its manufacturing, sales and R&D operations in Singapore.
- 2001 - Watlow moves to a new 20,000 square foot silicone rubber heater manufacturing facility in Anaheim, California. Watlow's Board of Directors appoints Peter Desloge to serve as the CEO of Watlow.
- 2002 - Watlow Process Systems moves to a new 50,000 square foot facility. Watlow launches Single Iteration as a new engineering services division, located in Fenton, Missouri. Watlow Engineering honored with "Technology & Business Vision" award by Start Magazine.
- 2003 - Watlow opens Watlow Iberica S.L., a new sales office in Madrid, Spain.
- 2004 - Watlow launches a smart sensing capability product line.
- 2005 - Watlow acquires Austrian-Based RHV Heizsysteme GmbH,for facilitating thermal spray technology.
- 2006 - Watlow introduces integrated controller technology with the new line of EZ-ZONE® controllers. Watlow opens a new manufacturing facility in Shanghai, China. Watlow develops and launches ULTRAMIC® advance ceramic heater technology. Watlow begins implementing Lean manufacturing throughout the organization.
- 2007 - Watlow opens a new Asia Application and Design Center in Singapore. Watlow opens a semiconductor technology design center in Los Gatos, California.
- 2008 - Watlow names Tom Lamantia as president.
- 2009 - Watlow receives Caterpillar® Inc. Supplier Quality Excellence Process certification.