Question: The Macau Peninsula has a gate built on the northern isthmus, for how long did it serve as a border?

Context paragraphs:
Macau–Taipa Line: Macau–Taipa Line () of Macau LRT a rapid transit line running circular in Macau Peninsula and U-shape in Taipa with a link between Macau Peninsula and Taipa under the Sai Van Bridge.

Guevea Zapotec: Guevea Zapotec, or Guevea de Humboldt Zapotec (Northern Isthmus Zapotec), is a Zapotecan language of the isthmus of Mexico.

Ilha Verde: Ilha Verde (), literally meaning "Green Island", is an area in the northwest of Macau Peninsula, Macau that forms part of the Our Lady Fatima Parish.  It was formerly an island to the west of the Macau Isthmus, and was connected to Macau Peninsula in 1895 when a causeway (now Avenida do Conselheiro Borja) was built.  Since then reclamation projects around the island took place and now it is annexed to be a part of Macau Peninsula.

Mochi Gate: The Mochi Gate locally known as Mochi Darwaza (Urdu: موچی گیٹ‎ ; ""Cobbler's Gate"") is located within the Walled City of Lahore in Lahore, Punjab, Pakistan.  Mochi Gate is a historical gate built by the Mughals.  It is at the site of one of the thirteen gates of the old walled city of Lahore.The Darwaza (Gate) used to exist next to the Laal Haveli, a prominent landmark at the entrance point.  In Urdu, Mochi means cobbler, which indicates that the bazaar was a market for shoes and repair shops.  Mochi Gate is also known for ancient Mosque of Muhammad Saleh Kamboh, teacher of Mughal Emperor Aurangzeb.

Macau Peninsula: Macau Peninsula is the most populous and historic part of Macau.  It has an area of 8.5 km² (4 x ) and is geographically connected to Guangdong province, at the northeast, through an isthmus 200 m wide.  The peninsula, together with the city centre of Zhuhai, sits on an island separated from the continent by distributaries of the Pearl River.  The Border Gate (; Portuguese: "Portas do Cerco" ) was built on the northern isthmus.  At the south, the peninsula is connected to Taipa Island by three bridges, the Friendship Bridge ("Ponte de Amizade"); the Macau-Taipa Bridge ("Ponte Governador Nobre de Carvalho"); and the Sai Van Bridge ("Ponte de Sai Van").  The longest axis extends 4 km from the Border Gate to the southwestern edge, Barra (媽閣嘴).  There is a western Inner Harbour (內港), and an eastern Outer Harbour (外港).  The 93 m Guia Hill (松山) is the highest point on the peninsula, which is, on an average, 50 to .  Many coastal places are reclaimed from sea.  The Historic Centre of Macau, which is entirely in the Macau Peninsula, became a World Heritage Site in 2005.

Battle of the Barrier: The Battle of the Barrier was fought between British and Chinese forces at the boundary separating Macau from the Chinese mainland on 19August 1840 during the First Opium War.  Located in modern-day Portas do Cerco, Macau was connected to China by a narrow isthmus about 100 m wide and 1.2 km long.  A wall called the "Barrier" was built across the isthmus in 1573, and it served as Macau's border.

Portas do Cerco: The Portas do Cerco is an area in Nossa Senhora de Fátima, Macau, China.  Located on the northern tip of the Macau Peninsula, it is known by its border gate separating Macau from mainland China.  The gate was built in 1849 to replace a crumbling wall that was erected in 1573 to mark the border of the Portuguese colony.  It was the site of the Passaleão Incident, a clash between the Qing dynasty and the Kingdom of Portugal in 1849 over the death of Macau's governor Ferreira do Amaral.  Led by Colonel Mesquita, Portugal won the small battle which led to the extension of Macau's border northwards.  At the limit of said expansion, the Portas do Cerco was built with the inscription "A pátria honrai, que a pátria vos contempla" (Portuguese for "Honor your motherland, for your motherland looks over you") on the façade on its inner arch in 1849.  For the next 155 years, the gate served as the border between Macau and China.

Macau Light Rail Transit: The Macau Light Rapid Transit or Macau LRT also known as Metro Ligeiro de Macau is a mass transit system in Macau under construction.  It will serve the Macau Peninsula, Taipa and Cotai, serving major border checkpoints such as the Border Gate, the Outer Harbour Ferry Terminal, the Lotus Bridge Border and the Macau International Airport.

Sai Van Bridge: Sai Van Bridge is a cable-stayed bridge in Macau, China, inaugurated on December 19, 2004.  The bridge measures 2.2 km long and is the third one to cross the Praia Grande Bay connecting Taipa Island and Macau Peninsula.  It features a double-deck design, with an enclosed lower deck to be used in the event of strong typhoons when the other two bridges connecting Taipa and Macau Peninsula, namely Ponte Governador Nobre de Carvalho and Ponte de Amizade, are closed.  Space is also reserved in the lower deck for a rail-link in the future (Macau Light Transit System).

Digha Gate: Digha Gate is an arcade or entrance gate built on the National Highway 116B.  It has been built in the beach city Digha of East Midnapore district, where the Digha-Shankarpur Development Board is built.  This huge arcade built in the entire point of the city of Digha, known as the Goa of Bengal.  The gate has been known as the "Gateway of Digha".

Supporting paragraphs: Macau Peninsula Portas do Cerco
Answer: 155 years