Then in 2011, the city and the Mural Arts Program asked them to make a similar splash along Germantown Avenue.
The murals are painted on about 50 storefronts in a four-block area between Cambria and Cumberland, said Jane Golden, executive director of Mural Arts.
"A major public-arts project could be the catalyst to related economic and community development," said Golden, who added that the project employed 20 people (six muralists and 14 neighborhood workers.)
The city was already planning to invest about $3.5 million to improve the storefronts, sidewalks and lighting in the area, said Alan Greenberger, deputy mayor for economic development.
Urhahn and Koolhaas lived and worked in the area for the past 18 months. Before either picked up a brush or drew a design, they lived in a house on Alder Street for six months as artists-in-residence at the Village of Arts and Humanities.
"We wanted to get to know the community, find out what colors the merchants wanted for their stores and learn the history of the neighborhood," Urhahn said.
They held barbecues and went to weddings and funerals. And Urhahn met his fiance at the Dew Drop Inn, a bar nearby.
While Koolhaas plans to return to Holland soon, Urhahn said he and his fiance will live in Philadelphia for a while.
Muhammad Custis, one of the neighborhood men working on the project, has a leadership role among the crew. He repaired many of the stores' facades to prepare them for painting.
"It means a lot to me to be able to do something constructive and positive for my community," said Custis, 28.
At Silver Street, Farhan Abusim, at the S&S Farmer's Market, praised the new look. But he and others want more than new paint.
"It's very nice," Abusim said. "But I hope now they will bring more security. I want to feel safe."
Even with the color, the buzz and the new energy that merchants say is evident, there are still too many robberies, Abusim said. He wants to see more police or security patrols.
"This is just one step," said Yonni Kim, owner of M.J. Apparel. "It's developing. It's nice that we now have the city's attention.
The project will be dedicated at
11 a.m. Saturday at 1007 W. Lehigh Ave., followed by a free tour.
On Twitter: @ValerieRussDN