DULUTH — One of Tom O'Rourke's favorite features of the newly completed expansion project at Hartley Park are the child-sized doors leading into the two new classrooms at the building that houses Hartley Nature Preschool.

"It's to help kids understand that this is their space, too," said O'Rourke, the nature center's executive director. The doorframe hits at about his elbow.

In the past three years there have been $3 million worth of updates to the 660-acre park in the northeast part of the city. There is new signage and maps on the sometimes confusing multiuse trails, pedestrian access from nearby Woodland Avenue and increased parking. The most significant change is the 5,000-square-foot addition to the 20-year-old nature center — which is for use by the public and the preschool.

Hartley's popular nature-based preschool opened in 2014, offering full- and half-day options for kids ages 3-5 during the school year. There is a wide variety of summer programming available, too, serving 1,100 young campers per season.

The waitlist for both runs deep.

"We felt squished," said O'Rourke. "We didn't have space to do what we needed to do."

Most of the preschoolers will shift to the new part of the building — which includes two classrooms, bathrooms and a conference room — keeping the original structure for visitors who might want to rent snowshoes or a kick sled, or gather for a group wildflower walk.

Hartley Nature Center is also a popular destination for school fieldtrips. O'Rourke said the site can now host 25 more students per trip.

Guilford Hartley bought 80 acres near Woodland Avenue in 1890, then added 700 more acres about a decade later. At the time, Greater Allandale Farm, as he called it, was the largest private farm in the city. Hartley died in 1922 and, after a significant tax increase on the property, his estate abandoned the fields. It became a city park in 1940.

Since the early 1980s, Hartley Park has been increasingly geared toward public recreation and education. It has 10 miles of multipurpose trails — the Superior Hiking Trail and the Duluth Traverse mountain bike trail run through it — and a fishing pond, a yurt, a playscape and a natural amphitheater. The original nature center, at 7,500 square feet, was built in 2003. The nonprofit environmental organization has a lease with the city that runs through 2053.

In 2019, the city of Duluth received $1.29 million from the Greater Minnesota Regional Parks and Trail Commission Legacy Grant geared toward improvements at the park, including increasing the size of the already 7,500-square-foot building. Hartley Nature Center raised $1,294,000 toward the project and received $450,000 from the Parks Capital Fund.

Hartley Nature Preschool offers outdoor-based play — one of a handful of similar preschools in the region. This year it grew by 30 students and four teachers. It was expected to shift into the new space this weekend.

The toilets here, too, are close to the ground — about shin-high. Earlier this week, a handful of preschool alums who are now elementary-school age were charged with the ceremonial ribbon cutting.

O'Rourke warned that they weren't safety scissors.

The preschoolers got a test run of the fresh space this week and were especially drawn to the new doors — including one decorated with a wreath saying "Welcome Owls" written in chalk.

"The kids enjoyed going through them," said preschool teacher Jen Petry.