Question: On what register is the 17 interconnected sculptural structures in Watts, Los Angeles listed in?

Context paragraphs:
Watts (Pacific Electric): The Watts line was a local line of the Pacific Electric Railway that operated between the Pacific Electric Building in Downtown Los Angeles, Los Angeles, California, United States and the Watts Station at 103rd Street in Watts, Los Angeles.  It was the primary local district service for the Southern District, which also included the Long Beach, San Pedro, Santa Ana and Whittier lines.  The route operated along the Southern Division's Four Tracks route, with the Watts Line using the outer tracks and the Long Beach line and other interurban and express lines using the inner tracks.  It operated between 1904 and 1958.  During the 1910s, its service was combined with the South Pasadena Line of the Northern District.  From 1938 to 1950, the line was combined with the Sierra Vista Line, which was the main local line in the Northern District.  Since 1990, service along the Watts Line between Washington Boulevard and 103rd Street has been operated by the Los Angeles Metro Blue Line, with stations at Washington Boulevard, Vernon Avenue, Slauson Avenue, Florence Avenue, Firestone Boulevard and 103rd Street.

Mujahid Abdul-Karim: Imam Mujahid Abdul-Karim (born Benjamin Farmer, December 26, 1944) is an African-American convert to Islam, who is best known for his involvement and "spearheading" of the April 26, 1992 Watts Gang Truce between the four influential rival gangs— Watts Hacienda Village Bloods, Grape Street Watts Crips, Bounty Hunter Watts Bloods, and PJ Watts Crips.  He is imam of Masjid Al Rasul mosque in Watts, Los Angeles and the leader of The Imam Mahdi Movement.

Watts Towers: The Watts Towers, Towers of Simon Rodia, or Nuestro Pueblo ("our town") are a collection of 17 interconnected sculptural structures within the Simon Rodia State Historic Park in the Watts community of Los Angeles.  The tallest of the towers reaches a height of over 99 ft .  The towers and walls were designed and built by Sabato ("Simon") Rodia (1879–1965), an Italian immigrant construction worker and tile mason, over a period of 33 years, from 1921 to 1954.  The work is an example of outsider art and Italian-American naïve art.

Watts, Los Angeles: Watts is a 2.12-square-mile neighborhood in Los Angeles, California, within the South Los Angeles region.  It is noted for the Watts Towers, which are a Los Angeles Historic-Cultural Monument and also listed on the National Register of Historic Places.

Susana Machado Bernard House and Barn: Susana Machado Bernard House and Barn is an elaborate 10000 sqft Art Nouveau Gothic Revival style mansion and carriage house located in the Pico Union section of Los Angeles, California.  Built in 1901, the house was designed by noted architect John B. Parkinson (1861–1935).  Parkinson also designed the Los Angeles Memorial Coliseum, Union Station and Los Angeles City Hall.  Noted for its Gothic style with soaring spaces, the house has vaulted ceilings and curved walls.  In 1979, it was designated a Los Angeles Historic-Cultural Monument (HCM #208), and listed on the National Register of Historic Places.  The property was purchased in 1996 by the Center for Human Rights & Constitutional Law.  Since 2002, the house has been operated as the Casa Libre/Freedom House, a fourteen-bed shelter for homeless minors.  In May 2003, the "Los Angeles Times" profiled the shelter, noting the following: "Casa Libre/Freedom House occupies a newly renovated mansion near MacArthur Park.  Registered as a state, county and federal historic site, the home's gothic facade rises elegantly from the corner of South Lake Street and James M. Wood Boulevard.  The shelter arranges for schooling, counseling, and medical care for undocumented and unaccompanied immigrant children, mainly from Latin America.

Watts truce: The Watts truce was a 1992 peace agreement among rival street gangs in Los Angeles.  It was declared between warring gangs in the community of Watts in the days just before the 1992 Los Angeles riots.  Although not universally adhered to, the truce was a major component of the decline of street violence in the city during the 1990s and 2000s.  After 20 years of internecine warfare that waged across the public housing projects of Los Angeles two rival sets within the infamous Crips gang decided to call a ceasefire.

Powder Magazine (Camp Drum): The Powder Magazine from Camp Drum is a Los Angeles Historic-Cultural Monument located in the Wilmington section of Los Angeles, California, near the Port of Los Angeles.  Built in 1862, the Powder Magazine is a 20 x brick and stone structure that was used to store gunpowder during the Civil War.  It was originally part of Camp Drum, a facility built upon the outbreak of the American Civil War to address concerns about the loyalty and security of the Los Angeles area.  Many of the area's residents were recent arrivals from the Southern states, and southerner John C. Breckinridge received twice as many local votes as Abraham Lincoln in the 1860 Presidential election.  Phineas Banning, the founder of Wilmington (then known as New San Pedro), wrote to President Lincoln advising that the Union would lose California unless some provision was made to quell pro-Confederacy sentiment.  Camp Drum was built between 1862 and 1863 and was the home base for the California Column, commanded by Colonel James Henry Carleton.  Between 2,000 and 7,000 soldiers were stationed at Camp Drum, and Wilmington became a thriving community with a population greater than Los Angeles during the war.  The Powder Magazine is one of only two surviving structures from Camp Drum, the other being the Drum Barracks, which is now operated as a Civil War museum by the City of Los Angeles.  The Powder Magazine has been used for various private uses over the years, at one point having another structure built around it.  When the larger structure was torn down, the Powder Magazine was re-discovered.  In order to save it from demolition, it was declared a Historic-Cultural Monument (HCM #249) in August 1982.  For more than two decades, it has sat on a vacant, fenced-off lot two blocks south of the Drum Barracks.

Watts Writers Workshop: The Watts Writers Workshop was a creative writing group initiated by screenwriter Budd Schulberg in the wake of the devastating August 1965 Watts Riots in South Central Los Angeles (now South Los Angeles).  Schulberg later said: "In a small way, I wanted to help... The only thing I knew was writing, so I decided to start a writers' workshop."  The group, which functioned from 1965 to 1973, was composed primarily of young African Americans in Watts and the surrounding neighborhoods.  Early on, the Workshop included a theatrical component and one of the founders was the actor Yaphet Kotto.  The group expanded its facilities and activities over the next several years with funding from the Rockefeller Foundation.  Government files later revealed that the Workshop had been the target of covert operations by the FBI.  Well-known writers to emerge from the Workshop include Quincy Troupe, Johnie Scott, Eric Priestley, Ojenke, Herbert Simmons, and Wanda Coleman, as well as the poetry group Watts Prophets.

Amoco Junction, Los Angeles: Amoco Junction was a junction on the Pacific Electric Railway's Southern District.  It was located in Nevin, South Central Los Angeles at 25th Street and Long Beach Avenue.  It was named after a nearby American Olive Company (AmOCo) plant.  It was the junction where the Santa Monica Air Line split off from the Watts, Long Beach and other Southern District Lines.  It was one of several points at which a tower crossed the quadruple tracks between Downtown Los Angeles and Watts.  Despite being a junction, many lines did not stop at Amoco, which was only served by local lines.  Service was provided to Amoco Junction between 1904 and 1958.  Though it is located along the route of the Los Angeles Metro Blue Line, it is not a stop or station on it, nor it is it a station on the Expo Line that replaced the Santa Monica Air Line.

Watts Station: Watts Station is a train station built in 1904 in Watts, Los Angeles, California.  It was one of the first buildings in Watts, and for many years, it was a major stop for the Pacific Electric Railway's "Red Car" service between Los Angeles and Long Beach.  It was the only structure that remained intact when stores along 103rd Street in Watts were burned in the 1965 Watts Riots.  Remaining untouched in the middle of the stretch of street that came to be known as "Charcoal Alley", the station became a symbol of continuity, hope, and renewal for the Watts community.  It has since been declared a Historic-Cultural Monument and is listed on the National Register of Historic Places.

Supporting paragraphs: Watts, Los Angeles Watts Towers
Answer: National Register of Historic Places