Question: The Chicago Maroons play their home games at a stadium that was named a Chicago Landmark in what year?

Context paragraphs:
Chicago Maroons women's basketball: The Chicago Maroons women's basketball team is an NCAA Division III college basketball team competing in the University Athletic Association.  Home games are played at the Gerald Ratner Athletics Center, located on the University of Chicago's campus in Chicago.

1905 Chicago Maroons football team: The 1905 Chicago Maroons football team represented the University of Chicago during the 1905 Western Conference football season.  In coach Amos Alonzo Stagg's 14th year as head coach, the Maroons finished with an 11–0 record (7–0 Western) and outscored opponents 271 to 5.  The Maroons were retroactively named national champions by the Billingsley Report, the Helms Athletic Foundation, the National Championship Foundation, and the Houlgate System.

Stagg Field: Amos Alonzo Stagg Field is the name of two different football fields for the University of Chicago.  The earliest Stagg Field (1893-1957) is probably best remembered for its role in a landmark scientific achievement by Enrico Fermi during the Manhattan Project.  The site of the first artificial nuclear chain reaction, which occured within the west viewing stands structure, received designation as a National Historic Landmark on February 18, 1965.  On October 15, 1966, which is the day that the National Historic Preservation Act of 1966 was enacted creating the National Register of Historic Places, it was added to that as well.  The site was named a Chicago Landmark on October 27, 1971.

1906–07 Chicago Maroons men's basketball team: The 1906–07 Chicago Maroons men's basketball team represented the University of Chicago in intercollegiate basketball during the 1906–07 season.  The team finished the season with a 21–2 record and were named national champions by the Helms Athletic Foundation.  This was the first of three consecutive seasons that Chicago claimed the Helms national championship.  The team played their home games on campus at Frank Dickinson Bartlett Gymnasium.

1908–09 Chicago Maroons men's basketball team: The 1908–09 Chicago Maroons men's basketball team represented the University of Chicago in intercollegiate basketball during the 1908–09 season.  The team finished the season with a 12–0 record and was retroactively named the national champion by the Helms Athletic Foundation and the Premo-Porretta Power Poll.  This was the third consecutive season for which Chicago was later named the Helms national champion.  The team played their home games on campus at Frank Dickinson Bartlett Gymnasium.

2015 Chicago Maroons football team: The 2015 Chicago Maroons football team represented the University of Chicago in the 2015 NCAA Division III football season.  The Maroons played in the Southern Athletic Association, their first season in the conference after having been in the University Athletic Association for the previous 24 seasons.  They were led by third-year head coach Chris Wilkerson and played their home games at the 1,650 seat Stagg Field, located on the west end of campus.

2014 Chicago Maroons football team: The 2014 Chicago Maroons football team represented the University of Chicago in the 2014 NCAA Division III football season.  The Maroons, having left the University Athletic Association the previous year, are playing as D-III Independents; the Maroons will be transitioning to the Southern Athletic Association next year.  They are led by second year head coach Chris Wilkerson and played their home games at the 1,650 seat Stagg Field, located on the west end of campus.

2016 Chicago Maroons football team: The 2016 Chicago Maroons football team represented the University of Chicago in the 2016 NCAA Division III football season.  The Maroons played in the Southern Athletic Association, their second and final season in the conference.  They were led by fourth-year head coach Chris Wilkerson and played their home games at the 1,650 seat Stagg Field, located on the west end of campus.

1907–08 Chicago Maroons men's basketball team: The 1907–08 Chicago Maroons men's basketball team represented the University of Chicago in intercollegiate basketball during the 1907–08 season.  The team finished the season with a 23–2 record and were named national champions by the Helms Athletic Foundation.  This was the second straight year that Chicago claimed the Helms national championship.  The team played their home games on campus at Frank Dickinson Bartlett Gymnasium.

Chicago Maroons: The Maroons are the intercollegiate sports teams of the University of Chicago.  They are named after the color maroon.  Team colors are maroon and gray, and the Phoenix is their mascot.  They now compete in the NCAA Division III, mostly as members of the University Athletic Association.  The University of Chicago helped found the Big Ten Conference in 1895; although it dropped football in 1939 (as inconsistent with its academic vision), its other teams remained members until 1946.  Football returned as a club sport in 1963, as a varsity sport in 1969, and began competing independently in Division III in 1973.  The school was part of the Midwest Collegiate Athletic Conference from 1976 to 1987, and its football team has joined the Midwest Collegiate Athletic Conference's successor, the Midwest Conference, as of the 2017 season.  Stagg Field is the home stadium for the re-instated football team.

Supporting paragraphs: Chicago Maroons Stagg Field
Answer: 1971