Works of art by Kenny Scharf and Okuda San Miguel adorn the interior of International Church of Cannabis in Denver. Credit: Marc Piscotty/Getty Images

For the International Church of Cannabis in Denver, there were three reasons to celebrate on Thursday.

First, it was opening day. The church, a more than century-old building recently adorned with brightly colored paintings by the artists Kenny Scharf and Okuda San Miguel, welcomed the public early in the afternoon, at which time no cannabis consumption was allowed inside.

“It seemed to be a nice steady flow of people,” said Lee Molloy, a founder of the church and a member, who estimated that a couple of hundred people had come by.

Second, it was April 20, an unofficial holiday of sorts for marijuana users. There have been disagreements as to why the number 420 has taken on significance in the cannabis community, but Steve Berke, the church’s media relations director, did not want to worry about that.

“It’s a number that everybody’s adopted, and we’re adopting it too,” he said. The church closed its doors to the public after 2 p.m. local time, leaving only invited visitors, who were allowed to light up for a private 4:20 ceremony.

And third: A challenge to the church’s legality, in the form of an amendment proposed in the state’s House of Representatives, was shut down almost as quickly as it arose on Thursday morning.