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Project Spotlight  ·  Custom Modular Buildings  ·  California 2026

Project Spotlight: Custom Modular Buildings at Dos Rios State Park

Two custom modular buildings, designed and factory built by API Trailers, now stand at Dos Rios State Park near Modesto. Here is what we built and what makes the park worth a visit.

Direct Answer

API Trailers designed, factory built, delivered, and set two custom modular buildings at Dos Rios State Park in Modesto: a 10×18 Entrance Center for check-in and a 10×22 Welcome Center, both with custom exterior and interior finishes. The park sits where the San Joaquin and Tuolumne rivers meet and opened to the public in June 2024. Call 805-328-6031 to talk about a custom building for your site.

Every park visit starts with a building: a place to check in, pick up a map, and ask a question. At Dos Rios State Park, two of those buildings came out of API’s factory. The park was built on the property long known as Dos Rios Ranch, and California State Parks describes it as California’s newest state park.

This spotlight covers what API built, the finishes you can see in the photos, and a few highlights of the park itself. To see more of our work, browse API’s modular buildings.

One of two custom modular buildings API Trailers built at Dos Rios State Park, with dark plank siding and a wood deck

A custom building on its wood deck at Dos Rios State Park

Custom modular building at Dos Rios State Park with glass double doors and a shed-style roof

Another exterior view, with glass double doors and windows

The Project at a Glance

LocationDos Rios State Park, Shiloh Road, Modesto, CA
BuildingsTwo custom buildings
Entrance Center10×18 check-in building (180 sq ft)
Welcome Center10×22 building (220 sq ft)
Design and BuildDesigned and factory built by API Trailers
DeliveryDelivered and set by API
FinishesCustom exterior and interior

What API Trailers Built at Dos Rios State Park

API built two custom buildings for Dos Rios State Park: a 10×18 Entrance Center for check-in and a 10×22 Welcome Center. The Entrance Center is the smaller of the two at 180 square feet, and the Welcome Center is 220 square feet.

Both buildings were designed and factory built by API, then delivered and set at the park. Both carry custom exterior and interior finishes.

Finishes You Can See in the Photos

  • Horizontal plank-style siding with black trim and black-framed windows
  • Black-framed glass double doors and a large opening on the front wall
  • A slatted ceiling with track and linear lighting
  • Plank-look flooring
  • A wall-mounted heating and cooling unit
  • Finished details such as an exit sign and a fire extinguisher cabinet
Side view of a custom modular building at Dos Rios State Park with a black-framed window and outdoor heating and cooling unit

Side view: black-framed window, electrical box, and outdoor heating and cooling unit, with the water beyond the deck

Interior of a custom building at Dos Rios State Park with a slatted ceiling, track lighting, and glass double doors

Interior: slatted ceiling, track lighting, glass double doors, and plank-look flooring

Ceiling detail inside a custom modular building at Dos Rios State Park with linear lighting and a wall-mounted heating and cooling unit

Ceiling detail: slatted ceiling with linear and track lighting

Have a park, campus, or public site that needs a custom building?

Call API Trailers with the use, size, site, and timeline. We will talk through what a custom building could look like.

Why a Factory-Built Building Works for a Park Site

A factory-built building is constructed indoors at API Trailers’ factory and delivered complete, which keeps the work on the park site to delivery and setting. That is how both Dos Rios buildings were done.

Site Work and Building Happen Together

While a building is built in API’s factory, site work can move ahead at the same time.

Custom, Not a Stock Plan

API customizes floor plans and finishes, which is how the Dos Rios buildings got their custom exteriors and interiors.

One Team From Design to Set

API designed, built, delivered, and set both buildings, so one company answers for the result.

Delivery Across California

Dos Rios is well north of API’s Santa Maria home base. API delivers anywhere in California with its own trucks, and delivery cost depends on distance.

Dos Rios State Park: Highlights

Dos Rios State Park is a park of about 1,600 acres, roughly 8 miles west of Modesto in Stanislaus County, where the San Joaquin and Tuolumne rivers meet. It opened to the public on June 12, 2024, according to California State Parks.

A Restored Floodplain

The park comes from a 10-year restoration funded from 11 public and private sources. State Parks calls it the largest public-private floodplain restoration project in California.

A New State Park

At its opening, State Parks called Dos Rios the state’s newest state park and the first new state park in 10 years.

Self-Guided Trails

The Pond Loop Trail is a 1.85-mile loop with a quarter-mile accessible section, and the Confluence Trail leads out to where the two rivers meet.

Wildlife

Dos Rios is a destination for birds migrating along the Pacific Flyway. A “bunny mound” shelters the endangered Riparian brush rabbit during flooding.

Picnicking

Base Camp, the day-use area, has newly built picnic tables and ramadas.

Dogs Welcome on Leash

Leashed dogs, on a leash no longer than 6 feet, are welcome at Base Camp and on the two trails.

Planning a visit? Hours, fees, events, and trail conditions change. Check the California State Parks Dos Rios page for current information before you go. Park details in this post come from California State Parks news releases and its Dos Rios page, reviewed in September 2026, and may have changed since.

More Custom Modular Buildings for Parks and Public Sites

Dos Rios is not API’s first State Parks project. API also built the California State Parks Nature Education Facility in Carpinteria, a two-piece permanent modular building with a classroom, office space, break room, and locker room, finished with custom-design cement siding. See the Carpinteria project page.

Other API buildings suit parks and public sites too. Guard houses work as entry booths, and custom cabin trailers are used at campgrounds and RV resorts.

Completed California Projects

  • UC Merced, University of California
  • Santa Rosa Fire Station
  • West Basin Municipal Water District, El Segundo
  • YMCA, Santa Maria
  • Regional Wastewater Training Facility, Santa Clara
  • Woods Humane Society, Atascadero
  • Crisis Stabilization Unit, San Luis Obispo
  • California State Parks, Carpinteria
  • Epoch Winery, Templeton
  • UCSB AS Bike Shop, Santa Barbara
  • Port of Long Beach
  • Cal Poly AG Department Housing, San Luis Obispo
  • New Cuyama Library
  • Payless Car Rental, South San Francisco
  • Santa Barbara County Fire Station, Sisquoc
  • USFS Rock Creek Barracks, Mammoth Lakes
  • Lompoc Foursquare Church
  • Paso Robles Horse Park

Frequently Asked Questions

What did API Trailers build at Dos Rios State Park?
API Trailers designed and factory built two custom buildings for Dos Rios State Park in Modesto, then delivered and set them at the park. One is a 10×18 Entrance Center for check-in, and the other is a 10×22 Welcome Center. Both have custom exterior and interior finishes.
How big are the Dos Rios buildings?
The Entrance Center is 10×18, which is 180 square feet, and the Welcome Center is 10×22, which is 220 square feet. Both were built in API Trailers’ factory.
Where is Dos Rios State Park?
Dos Rios State Park is about 8 miles west of Modesto in Stanislaus County, where the San Joaquin and Tuolumne rivers meet. It is a park of about 1,600 acres. Check California State Parks for current hours and visitor information.
When did Dos Rios State Park open?
Dos Rios State Park opened to the public on June 12, 2024. California State Parks described it at the time as the state’s newest state park and the first new state park in 10 years.
Does API Trailers build custom buildings for parks and public agencies?
Yes. Besides Dos Rios, API built the California State Parks Nature Education Facility in Carpinteria and has completed projects for fire stations, water districts, and universities. Requirements for public buildings vary by agency and location, so call 805-328-6031 to talk through your project.
Can API Trailers deliver a custom building anywhere in California?
Yes, API can deliver anywhere in California with its own trucks. Delivery cost depends on distance from the Santa Maria yard, and Dos Rios in Modesto is well north of it. Call 805-328-6031 with your address for a delivery quote.
Are API Trailers’ buildings custom or standard?
API builds both standard and custom buildings. The Dos Rios buildings have custom exterior and interior finishes, and API customizes floor plans on request.
How much does a custom building cost?
There is no single price. Cost depends on size, finishes, design, and delivery distance. Call 805-328-6031 for a quote scoped to your project.

Ready to talk about a custom building?

API Trailers builds custom buildings in its factory and delivers them across California. Tell us the use, size, site, and timeline.

805-328-6031 Request a Free Quote → sales@apitrailers.com 1916 W. Stowell Rd, Santa Maria, CA 93458
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