Question: What artist is best known for his design of the former estate of John Shaffer Phipps, heir to the U.S. Steel fortune?

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Mountain Iron Mine: The discovery of a boulder of high-grade iron ore by Leonidas Merritt in 1887 during a survey for the railroad, which he brought to Duluth, the Merritt brothers ("the Seven Iron Men") established the Mountain Iron Mine in 1892 Mountain Iron, Minnesota which represents the beginning of the exploitation of the Mesabi Range iron ore in the Iron Range of northeast Minnesota.  By 1893 the Merritts had claims on a significant portion of the Mesabi Iron Range and had built the Duluth, Missabe & Northern Railway DM&IR.  Financial conditions forced them sell their shares to John D. Rockefeller who later sold to Andrew Carnegie.  The early development was as an underground mine, but open cast mining soon proved to be a better choice because of the soft, shallow ore deposits.  The Mesabi Range and nearby Vermilion Range led Minnesota to become the nation's largest producer of iron ore and the United States to lead the world in steel production.  This capacity is considered to have been a major factor in America's ability to contribute to World War II.  It also played a major role in the financial success of Andrew Carnegie and U.S. Steel.  Carnegie returned some of his fortune to the communities by funding 2500 public Carnegie Libraries across the country, including 64 in rural Minnesota.

Ayavalla Plantation: Ayavalla Plantation was a quail hunting plantation located in northwest Leon County, Florida, established by John Henry Howard Phipps, son of John Shaffer Phipps of the prominent Phipps family.

Kingsley Plantation: Kingsley Plantation (also known as the Zephaniah Kingsley Plantation Home and Buildings) is the site of a former estate in Jacksonville, Florida, that was named for an early owner, Zephaniah Kingsley, who spent 25 years there.  It is located at the northern tip of Fort George Island at Fort George Inlet, and is part of the Timucuan Ecological and Historic Preserve managed by the U.S. National Park Service.

Winyah Park: Winyah Park (later known as Lathers Hill) was the 300-acre country estate of Colonel Richard Lathers, located in the village of New Rochelle, Westchester County, New York, upon which a number of 19th-century Gothic villas and cottages designed by Alexander Jackson Davis were built.  It was in 1848, after a brief but successful business career in New York, that, attracted by the accessibility and the natural environment of New Rochelle, Colonel Richard Lathers purchased a large country estate and farm along the New Rochelle and Pelham border.  Three years later, in 1851, Lathers employed his personal friend and renowned architect Alexander Jackson Davis to design him a more seemly and dignified residence than the old farmhouse which existed.  Revolutionizing the traditional single-house form that dominated colonial and early 19th-century domestic architecture, Davis was creating many of the country's finest villas and cottages in an entirely new, purely American style.  The residence designed for Lathers was the landmark brick and marble Italian villa "Winyah", named for Lathers former estate in Winyah Parish, South Carolina.

George A. Crawley: George Abraham Crawley (1864–1926) was a British artist, designer and purveyor of English taste.  He is best known for the design of John Shaffer Phipps' (the heir to a U.S. Steel Magnate fortune) home, Westbury House (built 1904–10; additions constructed in 1915–16), at Old Westbury Gardens, in Long Island, New York.

Mill House (Middleburg, Virginia): Mill House, also known as Chinn's Mill and Hatcher's Mill, is a historic grist mill complex located near Middleburg, Fauquier County, Virginia.  All of the buildings in the complex are constructed of stone laid in a random-rubble pattern and some are of mixed stone and frame construction.  They represent a late 18th- to early 19th-century rural Virginia grist mill operation, that was later transformed during the early-20th-century into a "hunt country" estate by John Shaffer Phipps.  In addition to the mill itself, the complex includes the miller's house, the cooper's house and shop, the mill owner's house, and what was likely a dairy/smokehouse.

Peter Muller-Munk Associates: Peter Muller-Munk Associates (known as PMMA) was an American industrial-design firm that flourished in Pittsburgh under the direction of its charismatic name partner.  PMMA's work touched almost every aspect of industrial design and were especially influential in the realm of consumer goods.  Notably, U.S. Steel hired PMMA to work on the general aesthetic design for the Unisphere, the theme center of the 1964 New York World's Fair.

Old Westbury Gardens: Old Westbury Gardens is the former estate of John Shaffer Phipps (1874–1958), heir to a U.S. Steel fortune, in Nassau County, New York.  Located at 71 Old Westbury Road in Old Westbury, the property was converted into a museum home in 1959 and is open for tours April through October for a fee.

John Shaffer Phipps: John Shaffer Phipps (August 11, 1874 – May 12, 1958) was an American lawyer and businessman who was an heir to the Phipps family fortune and a shareholder of his father-in-law's Grace Shipping Lines.  He was a director of the Hanover Bank, U.S. Steel Corp. and W. R. Grace & Co.

Charles J. Phipps: Charles John Phipps FSA, known as C.J. Phipps (1835 – 25 May 1897) was an English architect best known for his theatres.

Supporting paragraphs: George A. Crawley Old Westbury Gardens
Answer: George Abraham Crawley