It's an honor that has only been bestowed on 15 downtown areas in the state, according to Michael Garrigan, the village planner.
"This is a reflection of the continued renaissance of our downtown," Garrigan said.
Plainfield's National Register District runs along Lockport Street between Illinois Route 59 and James Street, according to the town, and includes 53 properties. Some of the notable buildings that helped Plainfield earn this designation include the Plymouth Congregational Church, the Clock Tower Building and the Masonic Lodge.
The area around Lockport Street features a variety of old buildings from varying times that showcase different architectural styles, Garrigan said.
"We have a variety of structures dating back to the 1840s," he said.
Some of the architectural styles that can be found in the area include Greek revival, Italianate, Queen Anne, Richardsonian Romanesque and International.
The process to get downtown Plainfield on the national register began last spring, Garrigan said.
First, the town applied for and received an Illinois Historic Preservation Agency grant.
Armed with the $15,000 grant, the town figured out where its historic downtown boundaries would like and hired an historic preservation consultant, Garrigan said.
The state agency handles the task of determining which towns can join the national register, he said.
"We had to show them that there was a significant and sufficient historical and architectural integrity to the district," Garrigan said.
Garrigan lauded the Village Board for supporting the preservation and restoration of Plainfield's oldest structures.
Board members have supported facade grants and other measures to enhance the historic flavor of the Lockport Street area, he said.
The new designation will also be a boon for the owners of those old buildings, as they will now be eligible for a 20 percent tax credit, which will also be available for anyone who has had work done on their building in the past five years, Garrigan said.
It is not always easy to keep a town's architectural history intact, Garrigan said.
Some buildings, like the old Baptist church that stood on the southwest corner of Lockport and Route 59, didn't get the preservation attention they deserved, he said.
"That was many, many boards ago," Garrigan noted. "We've had losses. Anybody who does preservation, there's always going to be steps back, some losses. That's the nature of the game."
The news comes a few weeks after the Village Board voted to designate the Ingersoll House on West Commercial Street as an historic landmark.
The house was built around 1834 and is one of the earliest structures to be erected in the town, according to village officials.