The Hayden Flour Mill is one of Tempe's most recognizable landmarks — and the reason the street it's on in downtown Tempe is named Mill Avenue. But it's also sat vacant for nearly two decades as the city has grown around it.

Now, as The Arizona Republic reported recently, the city is moving ahead with plans to reshape the historic mill into office and retail space, plus a five-story hotel, starting in 2018.

Tempe purchased the mill property in 2003 and agreed to lease it to Chicago-based Baum Development in 2016. The city approved the first phase of the mill's redevelopment last month, The Republic reported. Construction is slated to begin this year, with some amenities open by the summer of 2019 and the project completed by early 2021.

The mill's iconic grain silos will be reshaped into hotel rooms in the second phase of the project, the developer told The Republic, and the additional hotel building will be built behind the mill to avoid obstructing the view of the silos or the adjacent Hayden Butte, also known as Tempe Butte and "A" Mountain.

Milling operations began at the site in 1874, and the Hayden family, led by Tempe co-founder Charles Trumbull Hayden, managed it for three generations. The Hayden family also produced the late Carl Hayden, Arizona's longtime U.S. congressman and senator.

The current concrete structure dates to 1951; the original wood and adobe structure burned down in the 1910s. The site is listed on the National Register of Historic Places.