It's a major milestone for the Hepworth, which is halfway into its two-year build, and springing into shape on Wakefield Waterfront.
The new footbridge is 50m long, weighs 85 tonnes and took three hours to install.
Terry Hughes, project manager for The Hepworth contractor Laing O'Rouke, said: "Planning the lift of the bridge was critical – it has been very, very tight. We needed 200 tonnes of counter balance on the crane and we had a couple of delays but it's great to see people walking across it for the first time.
"The Hepworth is going to be an iconic building. The Concrete Society told me 'don't do it – it's impossible,' but we have and so far it looks great."
Once complete, the Hepworth will have international standing in the art world with an expected 150,000 visitors a year.
One of the highlights will be the Hepworth at Work gallery, with original plaster sculptures made by city-born Barbara Hepworth, some of her tools, and video footage of her at work.
Other galleries will feature Wakefield's huge art collection, including works by Henry Moore. Wakefield's current gallery can only show about five per cent of its collection at any time.
 There will also be a 100-seat auditorium, cafe and restaurant, education space and temporary gallery space.
Gallery director Simon Wallis said: "It's important for us to reclaim Barbara Hepworth for Wakefield, as she is so often associated with Cornwall, where she had a studio. The landscape influenced Hepworth and Moore, shaping their careers, and the future of British sculpture."
The next milestone in the development will be the removal of barriers keeping the river away from the gallery walls in February.
Once removed, the river will meet the side of the gallery, 16m above the heads of people working in the basement.