Cast-iron hot water and steam boilers are still made in the USA from iron poured in American foundries. Weil-McLain casts its own sections in Indiana, and U.S. Boiler Company builds its boilers in Pennsylvania from sections cast in Ohio.
A cast-iron boiler is mostly its iron heat exchanger sections; gas valves, controls and burners are often bought in. Each listing is rated for the company's most American-made line and says what is known to come from elsewhere.
Ranked by Made in USA level, highest first; ties are in alphabetical order. The level measures how much is made in the USA, not product quality. How the levels work
U.S. Boiler Company makes residential and commercial boilers for gas, oil and steam heat, including cast-iron boilers, the Alta condensing boiler and Burnham-brand boilers, plus indirect water heaters and baseboard radiators, sold through heating contractors. It is a subsidiary of Burnham Holdings in Lancaster, Pennsylvania.
U.S. Boiler's About page says, "Quality, made in America cast iron sections are produced for U.S. Boiler Company by Casting Solutions, another Burnham Holdings subsidiary, located in Zanesville, Ohio, USA," and calls itself "THE leading brand in hydronic heating ... Made in America!" Its products page says every boiler "is designed and assembled in Lancaster, Pennsylvania."
Gas valves, controls and burners are likely bought in. Where the stainless heat exchanger in its Alta condensing boiler is made isn't stated, though the company says the Alta is manufactured in Lancaster.
Production history: U.S. Boiler has built boilers in Lancaster for about a century; in 2025 it opened a 45,000 square foot Condensing Center of Excellence there and Burnham Holdings wound down its Crown Boiler plant in Philadelphia, moving that work to Lancaster. We found no move abroad.
Our rough estimate: imported or likely imported parts (gas valves, controls, burners and circulators) are about 15–30% of the value.
Level 4 for its cast-iron boilers assembled in Lancaster, Pennsylvania from sections cast in Zanesville, Ohio: U.S. Boiler assembles its boilers in Lancaster, Pennsylvania from cast-iron sections made by a sister company in Ohio; controls and valves are likely bought in.
Weil-McLain makes hydronic heating boilers for homes and commercial buildings, from cast-iron gas and oil boilers to high-efficiency condensing and combi boilers, plus indirect water heaters, sold through heating contractors. Founded in 1881, it is part of SPX Technologies.
Weil-McLain's About page says, "Manufacturing in Michigan City, Indiana for over 100 years, we have grown to be the largest U.S manufacturer of cast-iron boilers," with "an additional manufacturing location in Eden, North Carolina." A January 2026 job posting for a foundry supervisor (melt department) shows the Michigan City foundry still pouring iron.
Its site makes no plain "Made in USA" claim. Gas valves, controls and burner parts are likely bought in. Its condensing boilers use stainless or aluminum heat exchangers; heating forums report some are imported from Europe, which we couldn't confirm.
Production history: Weil-McLain has cast boilers in Michigan City since 1918; in 2005 it closed a Michigan plant and moved assembly and sheet metal work to Eden, North Carolina, keeping the foundry in Indiana. SPX has owned it throughout. We found no layoffs since 2011.
Our rough estimate: imported or likely imported parts (gas valves, controls, burner parts and circulators) are about 15–30% of the value.
Level 4 for its cast-iron gas and oil boilers, cast in Michigan City, Indiana: Weil-McLain casts the iron sections for its boilers at its own Michigan City, Indiana foundry and assembles them in Eden, North Carolina; controls and valves are likely bought in.
Cast iron is the American-made core. Both makers listed here cast their boiler sections in US foundries.
High-efficiency boilers are less certain. Condensing boilers use stainless or aluminum heat exchangers, and some are reported to come from Europe; ask about the model you're considering.
Controls and gas valves are usually bought in. That's what keeps these boilers from a 5.
Each listing's research notes show what was checked and when, including our rough estimate of how much of the value is imported.
Boiler makers by state
Indiana: Weil-McLain (Michigan City foundry; also Eden, North Carolina)
Pennsylvania: U.S. Boiler Company (Lancaster; sections cast in Zanesville, Ohio)
Change log
What's changed since our last review on July 12, 2017?
2 makers were re-checked, including where each has made its boilers over the years, and still build them in the USA: Weil-McLain and U.S. Boiler Company.
Every maker now has a Made in USA level from 0 to 5, with the sources and research notes behind it. See how the levels work.
Listings checked by Dave Hurley.
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A company may be based in the USA while making some products elsewhere. Check the manufacturer's own site for where a specific product is made.
