Millspaw Electronics, a Mason firm that keeps aging nuclear power plants running, landed the No. 2 spot among engineering companies on the 2026 Inc. 5000 list.

The company, headquartered at 5412 Courseview Drive, reported 756% revenue growth from 2022 to 2025, according to a Warren County Post report based on a company announcement. Millspaw ranked No. 457 overall among the 5,000 fastest-growing private companies in the United States. The median growth rate on the list was 130%.

Samuel Millspaw, president, sole owner and professional engineer, founded the company in 2019. He started his career as a procurement engineer at Bechtel, supporting the Naval Nuclear Propulsion Program, according to the company's website. He later served as lead repair engineer at ATC, now part of Paragon Energy Solutions, specializing in component repair and reverse engineering for safety-critical systems.

Millspaw Electronics repairs and refurbishes equipment for nuclear plants when original manufacturers stop making or supporting it. The company also engineers replacement parts that meet the nuclear industry's strict quality and documentation standards.

The company says it provides direct support to more than half of the 54 commercial nuclear power plants operating across 28 states. The U.S. nuclear fleet generates nearly 20% of the country's electricity, according to the World Nuclear Association. The industry spends about $8 billion a year on plant maintenance and upgrades.

The firm now has more than 30 employees. Vice President of Business Development Leigh Skorupskas, who joined in 2023, played a key role in building the company's nuclear quality assurance program. That program meets ASME NQA-1 and 10 CFR 50 Appendix B standards, which govern how components are designed, inspected, tested and documented for nuclear safety work.

"What matters is that we are there when a utility needs us, and that we keep looking ahead and building better systems so we can carry more of this industry's work than we could the year before," Skorupskas said in the company's announcement.

The growth is striking. Inc. magazine released the 2026 list on Aug. 11, ranking privately held, independent U.S. companies by three-year percentage revenue growth. Qualifying companies needed at least $100,000 in 2022 revenue and $2 million in 2025. The top 500 honorees, including Millspaw, will appear in the magazine's fall issue.