aid: day-zimmermann
name: Day & Zimmermann
url: >-
  https://raw.githubusercontent.com/api-evangelist/day-zimmermann/refs/heads/main/apis.yml
type: Index
position: Provider
access: 1st-Party
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
tags:
  - Ammunition
  - Architecture and Engineering
  - Construction
  - Defense
  - Engineering Services
  - Government Services
  - Industrial Services
  - Maintenance
  - Munitions
  - Nuclear Services
  - Power
  - Staffing
  - Workforce Solutions
created: '2026-05-22'
modified: '2026-05-23'
specificationVersion: '0.19'
kind: company
description: >-
  Day & Zimmermann is a privately held, family-owned diversified industrial
  services company founded in 1901 and headquartered in Philadelphia,
  Pennsylvania. The company operates across four primary business segments —
  Maintenance & Construction (power, nuclear, fossil, renewable, and chemical
  plants), Munitions (ammunition manufacturing, storage, and demilitarization
  for the U.S. military, including operation of the Lake City Army Ammunition
  Plant), Government Services (security, EOD, facility management, and
  architecture/engineering for federal agencies), and Workforce Solutions
  (staffing and talent placement via Yoh). The Yoh family has controlled the
  company since 1961; Harold L. Yoh III serves as Chairman and CEO. Day &
  Zimmermann reported approximately $2.7 billion in revenue in 2023 with
  roughly 43,000–52,000 employees across approximately 150 global locations.
  Day & Zimmermann does not publish any public developer APIs; its business is
  delivered through long-cycle service contracts, government-owned
  contractor-operated (GOCO) facilities, and direct client engagements.
apis: []
common:
  - type: Website
    url: https://www.dayzim.com
  - type: About
    url: https://www.dayzim.com/who-we-are/
  - type: Leadership
    url: https://www.dayzim.com/who-we-are/leadership/
  - type: History
    url: https://www.dayzim.com/who-we-are/history/
  - type: Maintenance and Construction
    url: https://www.dayzim.com/maintenance-and-construction/
  - type: Munitions
    url: https://www.dayzim.com/munitions/
  - type: Government Services
    url: https://www.dayzim.com/government-services/
  - type: Workforce Solutions
    url: https://www.yoh.com
  - type: Careers
    url: https://www.dayzim.com/careers/
  - type: News
    url: https://www.dayzim.com/news-and-events/
  - type: Contact
    url: https://www.dayzim.com/contact-us/
  - type: LinkedIn
    url: https://www.linkedin.com/company/day-&-zimmermann
  - type: Wikipedia
    url: https://en.wikipedia.org/wiki/Day_%26_Zimmermann
segments:
  - name: Maintenance and Construction
    description: >-
      Maintenance, construction, modification, and outage services for nuclear,
      fossil, and renewable power generation, plus chemical and industrial
      plants. Capabilities include welding, scaffolding, insulation,
      radiological protection, and turnkey plant services.
  - name: Munitions
    description: >-
      Ammunition manufacturing, loading, assembly, packing, storage, and
      demilitarization for the U.S. Department of Defense. Day & Zimmermann
      operates the Lake City Army Ammunition Plant in Independence, Missouri
      under a government-owned contractor-operated (GOCO) arrangement, producing
      small caliber ammunition (5.56mm, 7.62mm, .50 caliber) for the U.S. Army.
      Additional product lines include medium caliber rounds, warheads, fuzes,
      and direct/indirect fire munitions.
  - name: Government Services
    description: >-
      Integrated security services, explosive ordnance disposal (EOD), facility
      management, architecture, engineering, and commissioning for U.S.
      government agencies and federal installations.
  - name: Workforce Solutions (Yoh)
    description: >-
      STEM staffing and talent placement operated through Yoh, a Day &
      Zimmermann company. Service lines include IT, engineering, life sciences,
      and healthcare staffing, along with RPO (Recruitment Process
      Outsourcing), MSP (Managed Service Provider), and EOR (Employer of
      Record) workforce models. Yoh maintains 6,000+ active contractors.
subsidiaries:
  - name: Yoh
    description: STEM staffing and workforce solutions subsidiary.
    url: https://www.yoh.com
  - name: Day & Zimmermann NPS
    description: Nuclear power services division.
  - name: SOC LLC
    description: Government security services subsidiary.
customers:
  - name: U.S. Army
  - name: U.S. Department of Defense
  - name: U.S. Department of Energy
  - name: U.S. Nuclear Regulatory Commission-licensed utilities
  - name: Investor-owned utilities
  - name: Chemical and petrochemical operators
  - name: Federal civilian agencies
facilities:
  - name: Lake City Army Ammunition Plant
    location: Independence, Missouri
    role: Operator (GOCO)
    output: Small caliber ammunition for the U.S. Army
  - name: Corporate Headquarters
    location: Philadelphia, Pennsylvania
ownership:
  type: Privately held
  family: Yoh family (since 1961)
  chairman: Harold L. Yoh III
  founded: 1901
  founders:
    - Charles Day
    - Kern Dodge
    - John Zimmermann (joined 1907)
scale:
  revenue: ~$2.7B (2023)
  employees: ~43,000–52,000
  locations: ~150 global
  ranking: Ranked among Engineering News-Record Top 500 Design Firms
maintainers:
  - FN: Kin Lane
    email: kin@apievangelist.com