Former Carterton mayors Ron Mark, now deputy leader of NZ First, and Greg McPhee attending the opening.
Mr Booth said this was a very special occasion for Carterton and praised the "outstanding work" of the Carterton Lions Club, who developed the concept over two years.
"In particular, [statue convener] Alan Renall," said Mr Booth, saying without his commitment it would not have happened.
Mr Booth quoted Martin Luther King, saying: "We are not the makers of history; we are made by history."
"Carterton was made so much better by people like Charles Rooking Carter.
"We may only have 8800 residents, but we are growing, the number of new businesses is growing.
"We are a committed and engaged community."
He told Mr Key that Carterton had "done its bit to ease the Auckland housing problem.
"We are flattered by the number of people choosing to live here.
"We're a shining example of all that is good in New Zealand."
Mr Renall said the proudest part of the afternoon was having the prime minister attend, but confessed Mr Key was not their first choice.
"I said, let's go to the top of the tree - but we didn't know Richie [McCaw] was going to be busy flying helicopters or busy with his new fiancee."
He described Charles Rooking Carter as "an amazing and energetic man with a great vision".
His inspiration for a statue in Carterton came from seeing a bronze statue in Belgium and watching people pose beside it.
"I said, it had to be bronze, interactive, not just another perch for pigeons, and must be New Zealand-made.
"I believe this ticks all the boxes."
Mr Key was presented with Wairarapa steak by Mr Booth, "from the gate to the plate".
Across the road, two protesters, one describing herself as J R Murphy, Carterton poet, held up protest signs and sung songs.
Ms Murphy said the songs were about inequality.