Fall is a great time to visit Winterthur Museum, Garden, and Library, nestled in the rolling hills of the Brandywine Valley, about five miles from Wilmington, Delaware. In October and early November, thousands of trees—some centuries old—are in their autumnal glory. After November 21, grand fireplaces and cozy parlors are decked out for Yuletide, luring you in from the cold. Winterthur, about ninety minutes from New Hope, is celebrating its seventy-fifth anniversary this year with a series of exhibitions showcasing the history of the estate and its proudest feature: a world-renown collection of American furniture.

If you have time, stamina, and fair weather, you can walk from the visitor center through wooded gardens to the museum and back. But you’ll be relieved when a tram happens by to give you a lift. This place has 1,000 acres, and it’s hilly, so it’s easy to lose your way.

It’s best to get your bearings with a thirty-minute tour on the garden tram that departs regularly from the visitor center. Drivers will give you an overview of the landscape, views of the mansion and outbuildings from various angles, and quirky stories of how it all came to be.

Like Longwood Gardens, about eight miles away, Winterthur was a grand country estate established by the du Pont family, who settled along the Pennsylvania/ Delaware border southwest of Philadelphia in the early 1800s. Henry Francis du Pont (owner of Winterthur) and Pierre S. du Pont (owner of Longwood), cousins born in the late nineteenth century, both opened their family estates to the public in the 1950s.

Longwood is showier, known for fountain light shows and acres of formal gardens. It’s also more crowded, especially during the holidays, when scheduled visits sell out. Winterthur is older (by a century) and quieter, more museum than country house. Its gardens are more naturalistic and less colorful—except in spring and fall. Autumn brings an explosion of color. A fter leaving France to establish gunpowder mills in the Delaware countryside—the first of many successful du Pont family businesses—Éleuthère Irénée du Pont purchased the initial 475 acres that would become the nucleus of Winterthur, acquiring the land between 1810 and 1818. The du Ponts became one of the wealthiest dynasties in America and remain so to this day.

Winterthur is known locally as a peaceful getaway, with paved pathways winding through verdant landscapes that reveal the occasional treasure: a reflecting pool, a stone footbridge, an “enchanted woods” designed for children. (On the tram I encountered a couple of very small princesses who told me it’s their favorite place in the world.)

Henry Francis du Pont, born into massive wealth, was the third generation to live at Winterthur. With a degree in horticulture from Harvard, his first interest was the gardens, many of which he designed and planted himself. While raising two young daughters, he began breeding Holstein cattle in 1917, listing himself as a farmer on his tax returns.

In the early 1920s, he discovered some fine American-made antiques at a friend’s farmhouse in Vermont. Until then, he had thought of fine furniture as something made overseas.

He began to collect—with a passion. In 1929, he paid $44,000 (equivalent to nearly a million dollars today) for a high chest made in Pennsylvania. “That made national news at the time, because how could anyone pay that for an American object?” says Alexandra Deutsch, director of collections at Winterthur.

By the time du Pont opened Winterthur to the public in 1951, he had amassed one of the most important collections of American decorative arts in the world. To his surprise, curious visitors showed up in hordes. So did academics. He began hiring experts to curate, document, and expand his collection.

Winterthur now has more than 90,000 treasures in its permanent collection, many of which are displayed in the sprawling 175-room mansion. Winterthur grows the collection thanks to the generosity of donors of objects and purchases made possible through funds designated for that purpose.

What you’ll find at Winterthur is a deep dive into the history of the American aesthetic, housed in one of the country’s grandest country estates. One section is essentially a massive house tour of the highest order. On one level is a recreated village street, lined with shops and street lamps. The galleries are accessed through a separate entrance, with two levels of rotating exhibitions.

You can take a self-paced tour of the house, starting at the conservatory and, with the help of signage and a grounds map, find your way to various themed rooms. Trained guides sit in each, ready to answer questions. They know every juicy backstory and help bring order to the overwhelm you can feel walking through this place.

The structure of Winterthur was expanded many times to hold the insane amount of objects its final owner accumulated in his lifetime. It’s not only American decor. One of the coolest rooms is the Chinese parlor, covered with hand-painted wallpaper and furnished with Chinese exports. “Challenging Masterpieces: Art and Identity in American Furniture” opens September 26, showcasing more than seventy of the finest pieces from the collection.

When du Pont began collecting, America was still establishing an identity, starting to claim a place among the global idea of “masterpiece.” In du Pont’s lifetime, Deutsch says, “The idea of the relic—you know, great-grandfather’s old chair or the chair where Washington sat in the tavern—began to morph into what we now think of as a masterpiece.

“Mr. du Pont was a man of his time, raised in the Gilded Age. He preferred furniture built before 1815. The initial cutoff date for the collection was 1840, yet he collected many things that dated beyond that. Ultimately, he wanted Winterthur to be a place of teaching and learning. Over the years, generations of curators have built on that tradition.”

“Challenging Masterpieces” includes a couple new acquisitions Deutsch suspects du Pont would not have approved, including a polychrome-painted stand made in Maine. “There will be people who say that is not a masterpiece,” Deutsch says. “Mr. du Pont might have agreed with them, but he would have appreciated the conversation.”

Cathleen McCarthy has written about the arts and travel for the Washington Post, Town & Country, and the Wall Street Journal.