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Junior Developer Jobs in O Fallon, IL (NOW HIRING)

WSP

Junior Substation Designer

Saint Louis, MO

WSP is currently initiating a search for a Junior Substation Designer for our Minneapolis, MN ... Under minimal supervision, work closely with engineers to resolve design details or discrepancies ...

Dreams 2 Reality Recruitment

MEP Engineer

Saint Louis, MO · On-site +1

$120K - $150K/yr

  • Medical

  • Dental

  • Vision

  • Life

  • Retirement

  • PTO

Serve as the electrical design lead, providing direction to designers, drafters, and junior engineers. * Coordinate with architects, engineers, contractors, clients, and internal teams. * Establish ...

Stellar IT Group

Software Engineer

Saint Louis, MO · On-site

Mentor junior engineers and contribute to team growth through knowledge sharing and technical guidance. * Optimize application performance, scalability, and reliability. * Participate in code reviews ...

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All JobsDeveloper JobsJunior Developer JobsJunior Developer Jobs in O'Fallon, IL

Junior Developer information

See O Fallon, IL salary details

$22.4K

$83K

$128.3K

How much do junior developer jobs pay per year?

As of Aug 17, 2026, the average yearly pay for junior developer in O'Fallon, IL is $82,997.00, according to ZipRecruiter salary data. Most workers in this role earn between $62,500.00 and $81,200.00 per year, depending on experience, location, and employer.

What are the key skills and qualifications needed to thrive as a junior developer, and why are they important?

To thrive as a Junior Developer, you need a solid understanding of programming fundamentals, basic knowledge of software development life cycles, and ideally a degree in computer science or a related field. Familiarity with coding languages like JavaScript, Python, or Java, as well as version control systems such as Git, is commonly expected. Strong problem-solving abilities, eagerness to learn, and effective communication help you integrate into teams and adapt to new challenges. These skills are crucial for producing quality code, collaborating with colleagues, and growing within the fast-paced tech environment.

How much does a junior developer earn?

A junior developer typically earns between $50,000 and $70,000 annually, depending on location, industry, and skills. Entry-level roles often require knowledge of programming languages like Java, Python, or JavaScript, and familiarity with development tools and frameworks.

What is a junior developer?

A Junior Developer is an entry-level software professional who assists in creating, testing, and maintaining software applications. They typically work under the supervision of more experienced developers, learning best practices and acquiring new technical skills on the job. Junior Developers are expected to write code, fix bugs, and contribute to project documentation while gradually gaining experience in software development processes. This role is ideal for recent graduates or individuals transitioning into the tech industry.

What is the difference between Junior Developer vs Software Engineer?

AspectJunior DeveloperSoftware Engineer
Required CredentialsTypically an associate degree or bootcamp certificationBachelor's degree in Computer Science or related field
Work EnvironmentEntry-level, supervised tasks, learning-focusedMore complex projects, often with team leadership responsibilities
Employer UsageCommon in startups, small companies, internshipsUsed across industries, larger companies, and tech firms
Search & Comparison IntentUnderstanding entry-level roles, career startClarifying career progression, skill requirements

In summary, Junior Developers are entry-level roles focused on learning and supporting development tasks, often requiring minimal experience. Software Engineers typically have more experience, advanced skills, and handle complex projects, making them a step up in the software development career path.

What are some common challenges faced by junior developers during their first year, and how can they overcome them?

Junior Developers often face challenges such as adapting to new codebases, understanding company workflows, and bridging the gap between academic knowledge and real-world applications. It’s common to feel overwhelmed by unfamiliar technologies or debugging complex issues. Overcoming these challenges involves proactively seeking mentorship, participating in code reviews, and consistently asking questions to clarify concepts. Building strong communication skills and collaborating with more experienced team members can also accelerate the learning process and help you grow more confident in your role.

What does a junior developer do?

A junior developer assists in designing, coding, testing, and maintaining software applications under the supervision of senior developers. They typically work with programming languages like Java, Python, or JavaScript and use development tools such as version control systems. Their role involves learning best practices and gaining experience to develop their technical skills.

What cities near O'Fallon, IL are hiring for Junior Developer jobs?

Cities near O'Fallon, IL with the most Junior Developer job openings:

Junior Developer jobs near you
Infographic showing various Junior Developer job openings in O'Fallon, IL as of August 2026, with employment types broken down into 78% Full Time, 7% Part Time, 14% Contract, and 1% Nights. Highlights an 81% Physical, 4% Hybrid, and 15% Remote job distribution, with an average salary of $82,997 per year, or $39.9 per hour.

Project Engineer III/IV - Water/Wastewater

Trilon

Saint Louis, MO • On-site

$40 - $55/hr

Full-time

Medical, Dental, Vision, Retirement, PTO

Re-posted 22 days ago

Job description

Gonzalez Companies is a partner managed firm that provides comprehensive Planning, Design, and Construction Management Services to large and small Water, Sewer and Utility Districts; Departments of Transportation; and municipalities. We are currently seeking a Project Engineer (III/IV) - Water/Wastewater to help serve our connection of clients and community. If you're hungry for knowledge, ready to make a difference and dedicated to providing personalized attention to our clients, we want you on our team. 
The base salary range for this role is indicated in the posting. This range reflects the company's good faith estimate of the compensation for this position at the time of posting. Final compensation will be determined based on factors such as experience, skills, qualifications, internal equity, and geographic location.
  • Lead the design, analysis, and technical oversight of water and wastewater treatment facilities, pump stations, pipelines, and related infrastructure.
  • Prepare and review engineering calculations, design drawings, specifications, and technical reports.
  • Conduct hydraulic modeling and system analysis to optimize water distribution and sewer collection networks.
  • Manage field investigations, site assessments, and construction observation; provide technical guidance to junior engineers.
  • Develop project scopes, cost estimates, schedules, and proposals; support project management activities.
  • Coordinate multidisciplinary teams to ensure integrated and compliant project designs.
  • Review and ensure compliance with design standards, regulatory requirements, and permitting processes.
  • Serve as a point of contact for clients, contractors, and regulatory agencies; communicate technical information clearly and effectively.
  • Mentor and support junior staff; uphold quality control and company engineering standards.

  • Bachelor's degree in Civil, Environmental, or related engineering field.
  • EI/EIT required; PE registration preferred or in progress.
  • 4-8+ years of experience in water/wastewater design, permitting, or construction support.
  • Proficiency with hydraulic modeling tools (WaterGEMS, SewerGEMS, InfoWater, SWMM, etc.).
  • Strong experience with AutoCAD/Civil 3D; BIM/Revit knowledge preferred.
  • Demonstrated experience with pump systems, process equipment, site layout, and utility design.
  • Excellent analytical, project management, and problem-solving skills.
  • Strong leadership, communication, and client coordination abilities; capable of mentoring junior engineers.

  • Competitive salary
  • Major medical, dental and vision insurance
  • Flexible Spending Account
  • Health Savings Account
  • 401K
  • Bonus program
  • Paid holidays and generous paid time off
  • Professional development
  • A team of creative and talented individuals to work alongside
Gonzalez is a rapidly growing, dynamic, professional services firm specializing in civil engineering, construction management, and construction inspection. Our clientele includes large and small water, sewer, and utility districts; departments of transportation and other public transportation agencies; and municipalities throughout the Midwest.
Working primarily in the Greater St. Louis, Chicago, and Louisville metro areas, Gonzalez offers a great work environment, generous benefit packages, and opportunities to succeed in many professional disciplines.
Equal Opportunity Employer
Gonzalez Companies, LLC provides equal employment opportunities to all employees and applicants for employment and prohibits discrimination and harassment of any type without regard to race, color, religion, age, sex, national origin, disability status, genetics, protected veteran status, sexual orientation, gender identity or expression, or any other characteristic protected by federal, state or local laws.
This policy applies to all terms and conditions of employment, including recruiting, hiring, placement, promotion, termination, layoff, recall, transfer, leaves of absence, compensation and training.
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