Question: When did the province that Rustico-Emerald is part of become a province?

full_context: Document 1: Summerside-Wilmot: Summerside-Wilmot is a provincial electoral district for the Legislative Assembly of Prince Edward Island, Canada. It was formerly named Wilmot-Summerside from 1996 to 2007.
Document 2: Geography of Prince Edward Island: Prince Edward Island's geography is mostly pastoral with red soil, white sand, and scattered communities. Known as the "Garden of the Gulf", the island is located in the Gulf of Saint Lawrence north of Nova Scotia and east of New Brunswick, with which it forms the Northumberland Strait.
Document 3: Lennox Island (Prince Edward Island): Lennox Island is an island located in Malpeque Bay off the northwest coast of Prince Edward Island, Canada. Connected by a short causeway and bridge, Lennox Island is home to the Lennox Island First Nation, of the Mi'kmaq people. The Mi'kmaq name for the island was "L'nui Minegoo", and it has been informally known by European settlers as "Indian Island".
Document 4: Charlottetown-Brighton: Charlottetown-Brighton is a provincial electoral district for the Legislative Assembly of Prince Edward Island, Canada. It was formerly named Charlottetown-Rochford Square from 1996 to 2007.
Document 5: Confederation Trail: Confederation Trail is the name for a 470 kilometre recreational rail trail system in the Canadian province of Prince Edward Island.
Document 6: Pictou Island (Nova Scotia): Pictou Island is a Canadian island located in the Northumberland Strait approximately 4 NM north of Nova Scotia and 10 NM south of Prince Edward Island. Measuring 9.5 km in length and 2.5 km in width, the total area is 23.75 km. The island is administratively part of Pictou County. The island's highest elevation is 24 meters (78 feet) above sea level, and its current full-time residents population (as of 2016) stands at 28, with the seasonal population rising and lowering.
Document 7: Cornwall-Meadowbank: Cornwall-Meadowbank is a provincial electoral district for the Legislative Assembly of Prince Edward Island, Canada. It was previously known as North River-Rice Point.
Document 8: Province House (Prince Edward Island): Province House is where the Prince Edward Island Legislature, known as the Legislative Assembly of Prince Edward Island, has met since 1847. The building is located at the intersection of Richmond and Great George Streets in Charlottetown; it is Canada's second-oldest seat of government.
Document 9: Tignish-Palmer Road: Tignish-Palmer Road is a provincial electoral district for the Legislative Assembly of Prince Edward Island, Canada. It was formerly Tignish-DeBlois from 1996 to 2007.
Document 10: Charlottetown (electoral district): Charlottetown (formerly Hillsborough) is a federal electoral district in Prince Edward Island, Canada, that has been represented in the House of Commons of Canada since 2004. The district, which includes the entire City of Charlottetown, has an area of 46 km and a population of 34,562 as of 2011.
Document 11: Charlottetown-Victoria Park: Charlottetown-Victoria Park is a provincial electoral district for the Legislative Assembly of Prince Edward Island, Canada. It was previously known as Charlottetown-Kings Square.
Document 12: Rustico-Emerald: Rustico-Emerald is a provincial electoral district for the Legislative Assembly of Prince Edward Island, Canada. It was formerly known as Park Corner-Oyster Bed.
Document 13: Prince Edward Island: Prince Edward Island Île - du - Prince - Édouard (French) Epekwitk (Mi'kmaq) Flag Coat of arms Motto (s): Latin: Parva sub ingenti (The small protected by the great) BC AB SK MB ON QC NB PE NS NL YT NT NU Confederation July 1, 1873 (8th) Capital Charlottetown Largest city Charlottetown Largest metro Charlottetown Government Lieutenant Governor Antoinette Perry Premier Wade MacLauchlan (Liberal) Legislature Legislative Assembly of Prince Edward Island Federal representation (in Canadian Parliament) House seats 4 of 338 (1.2%) Senate seats 4 of 105 (3.8%) Area Total 5,660 km (2,190 sq mi) Land 5,660 km (2,190 sq mi) Water 0 km (0 sq mi) 0% Area rank Ranked 13th 0.1% of Canada Population (2016) Total 142,907 Estimate (2018 Q1) 152,768 Rank Ranked 10th Density 25.25 / km (65.4 / sq mi) Demonym (s) Prince Edward Islander, Islander Official languages English (de facto) GDP Rank 10th Total (2011) C $5.353 billion Per capita C $36,740 (13th) Time zone Atlantic: UTC - 4 Postal abbr. PE Postal code prefix ISO 3166 code CA - PE Flower Pink lady's slipper Tree Red oak Bird Blue jay Website www.princeedwardisland.ca Rankings include all provinces and territories
Document 14: Churchill, Prince Edward Island: Churchill is a community in the Canadian province of Prince Edward Island. The community was named for Winston Churchill. It is located in the township of Lot 65, Queens County immediately west of New Haven.
Document 15: Prince Edward Island: Prince Edward Island (PEI or P.E.I.; French: Île - du - Prince - Édouard) is a province of Canada consisting of the island of the same name, and several much smaller islands. Prince Edward Island is one of the three Maritime Provinces and is the smallest province in both land area and population. It is part of the traditional lands of the Mi'kmaq, and became a British colony in the 1700s and was federated into Canada as a province in 1873. Its capital is Charlottetown. According to the 2016 census, the province of Prince Edward Island has 142,907 residents.
ground_truth: 1873
sub_queries: Rustico-Emerald >> located in the administrative territorial entity Answer: Prince Edward Island
when did Prince Edward Island become a province Answer: 1873