Question: What year was the Johnson house built? 

Context paragraphs:
Glass House: The Glass House or Johnson house, is a historic house museum on Ponus Ridge Road in New Canaan, Connecticut.  Built in 1949, it was designed by Philip Johnson as his own residence, and "universally viewed as having been derived from" the Farnsworth House design, according to Alice T. Friedman.  Johnson curated an exhibit of Mies van der Rohe work at the Museum of Modern Art in 1947, featuring a model of the glass Farnsworth House.  It was an important and influential project for Johnson and for modern architecture.  The building is an essay in minimal structure, geometry, proportion, and the effects of transparency and reflection.  The estate includes other buildings designed by Johnson that span his career.  It was designated a National Historic Landmark in 1997.  It is now owned by the National Trust for Historic Preservation, and is open to the public for guided tours, which begin at a visitors center at 199 Elm Street in New Canaan.

Newell D. Johnson House: The Newell D. Johnson House is a historic house at 428 Lexington Street in Waltham, Massachusetts.  The 2-1/2 story wood frame house was built in 1894, and is one of the most elaborate Queen Anne houses in the city's Piety Corner neighborhood.  It has an octagonal tower at one corner with a pyramidal roof, bands of decorative cut wood shingling, and fluted porch posts.  Newell Johnson, a dentist, had thi house built on the site of the Sanderson House, one of the first to be built in the area.

Goldsmith C. Gilbert Historic District: Goldsmith C. Gilbert Historic District is a national historic district located at Muncie, Delaware County, Indiana.  It encompasses 75 contributing buildings and is located in the oldest residential section of Muncie.  The district includes notable examples of Late Victorian, Colonial Revival, and Bungalow / American Craftsman style architecture.  Located in the district is the separately listed J.C. Johnson House.  Other notable buildings include the A.L. Johnson House, Meeks Mortuary Building, Joseph Hummel House, and Miller Livery (1916).

Smith–Johnson House: The Smith–Johnson House, also known as The Old Brick, is a historic residence located in Oskaloosa, Iowa, United States.  It was built for William T. Smith in 1853, the same year he was elected as the first mayor of Oskaloosa.  A lawyer, Smith was a native of Pennsylvania who settled in the town in 1848 and became county attorney the same year.  In addition to his political and legal responsibilities he founded the first bank in town, and he was involved with other profitable financial ventures.  He lived in the house until 1865 when Abijah Johnson, a Quaker merchant who moved to Oskaloosa to be a part of the flourishing Quaker communities here and in the surrounding areas.  His son J. Kelly Johnson, an attorney who served in the Iowa Senate, took over the house after his father's death in 1894.

Mont and Harriet Johnson House: The Mont and Harriet Johnson House, at 153 E 400 N in Springville, Utah, United States, is a Late Victorian-style house built in 1901.  It was listed on the National Register of Historic Places in 1998.  The listing included three contributing buildings.

Booth House (Bedford, New York): The Booth House is a single-story modernist house in Bedford, New York.  Built in 1946, the house was American architect Philip Johnson's first residential commission, and is a stylistic precursor to Johnson's better-known 1949 Glass House in New Canaan, Connecticut.

Clear Run: Clear Run is a historic rural crossroads community located on the Black River at Clear Run, Sampson County, North Carolina.  The community includes 22 contributing buildings and 6 contributing sites.  Notable contributing resources include the Marvin Johnson House (c. 1898), Federal Herring House (1830s), the Colonial Revival style A. J. Johnson House (1909), Clear Run Grocery, furniture store (c. 1870), cotton gin, and the remains of the steamer "A. J. Johnson".

Olof Johnson House: The Olof Johnson House is a historic house located at 408 NW 4th Street in Galva, Illinois.  The house was built in 1863 for Olof Johnson, one of the trustees of the Bishop Hill Colony.  In addition to his position within the colony, Johnson also played a significant role in Galva's founding and named the community after his birthplace of Gävle, Sweden.  Johnson's house has an Italianate design, a popular style in the late 19th century.  The house's wraparound front porch is supported by thin columns and features paired brackets along its roof; similar brackets can be found on the eaves of the house's cross gabled roof.

John Johnson House (Leighton, Alabama): The John Johnson House also known as The Green Onion is a historic residence near Leighton, Alabama.  The house was built in the late 1820s by John Johnson, a settler from Mecklenburg County, Virginia, who lived in Middle Tennessee before coming to North Alabama.  His son-in-law, Lewis Dillahunty, was one of the earliest settlers in the western Tennessee Valley, and convinced Johnson to move to the area.  Johnson died in the early 1840s, and his son sold the house and 80 acres (32 ha) out of the family.  The house has been long occupied by tenant farmers, and is now part of the Leonard Preuitt estate.

John Johnson House (Philadelphia, Pennsylvania): The John Johnson House (also known as the Johnson House) is a National Historic Landmark in the Germantown section of Philadelphia, significant for its role in the antislavery movement and the Underground Railroad.  It is located at 6306 Germantown Avenue and is a contributing property of the Colonial Germantown Historic District, which is also a National Historic Landmark.  It is operated today as a museum open to the public.

Supporting paragraphs: Booth House (Bedford, New York) Glass House
Answer: 1946