The work of late gay rights activist and politician Harvey Milk will be celebrated in San Francisco's famous Castro District with a large set of ramping steps, designed by US architecture firm Perkins Eastman.

The stepped memorial will be built on Harvey Milk Plaza, an open square named to commemorate of Milk and his work in the 1970s as an activist for LGBTQ (lesbian, gay, bisexual, trans and queer) rights in the city.

Perkins Eastman won a contest organised by Friends of Harvey Milk Plaza to revamp the square, located at the intersection of Market, Castro and 17th Streets in The Castro – a hub for San Francisco's LGBTQ community.

Previously marked by a rainbow flag – the universal symbol of LGBT pride, which will remain on the site – the sloped plaza along Market will now feature a series of ramps that also form steps as they dogleg up the hill. A timeline marking key events in Milk's life and career will follow the path, while bright orange flooring will be used either side.

"The new Harvey Milk Plaza is reimagined as a vibrant, active, living place that more fittingly honours Harvey Milk's charismatic spirit and legacy as a community energiser and a vocal activist," said Perkins Eastman.

"The new Harvey Milk Plaza is a place that allows for and encourages political activism, community interactions, and the unfiltered display of self."

Celebrated as America's first gay neighbourhood, the Castro District became home to gay servicemen who chose to settle in San Francisco in the 1960s, after they were discharged from the US military because of their sexuality.

At the same time, many families were moving from The Castro for the suburbs, leaving property open to be purchased by the new residents.

Milk was among those who migrated to the neighbourhood, arriving in 1972. He quickly became interested in politics and campaigning for equal rights within the community, describing himself as its mayor.

Milk was appointed as a member of the San Francisco Board of Supervisors in 1978, making him the first openly gay person to be elected to public office in California. He was assassinated in the same year at 48 years old.

Perkins Eastman's San Francisco team was selected above 33 other entrants to complete the memorial in his honour.

As well as the timeline of events, which will also track progression in civil and LGBTQ rights following his death, Perkins Eastman's steps will form outdoor seating facing an open gathering spot and performance area at the base. Benches will provide places of pause along the way, while the top will form a look-out point with views across the surroundings.

Glazing will be slotted underneath the stairs, where escalators will lead down to an art gallery connecting to the Castro metro station.

The unveiling of the design comes as Friends of Harvey Milk Plaza celebrates the 40th anniversary of Milk's election to office, on 8 November 2017, and the 20th anniversary of first raising of the rainbow flag in the square.

The flag has become an iconic design, and is included in the permanent collections of New York's MoMA and London's Design Museum. As a tribute to its designer Gilbert Baker, who died earlier this year, ad agency Ogilvy & Mather created a colourful font to commemorate his achievements.