The two-day trip, which also included First Deputy Mayor Andrew Frank and other city officials, was set so that Dixon and other key officials could learn about Chicago's environmentally friendly initiatives.
The trip was funded with contributions from Gallagher, Evelius and Jones, a law firm that has represented clients in lawsuits against the city; the Parks & People Foundation; the Downtown Partnership; a foundation tied to M&T; Bank; and the Waterfront Partnership.
The mayor's office did not include the trip in Dixon's public schedule, and the administration first announced it with a news release hours after she had arrived in Chicago.
A City Hall spokesman said about $5,000 in private money was raised for the trip, and that no taxpayer money was spent.
"I am looking forward to learning about how Chicago has implemented their plan to create long-term environmental stability for their communities," Dixon said in a statement. "If we are to achieve a cleaner, greener, and ultimately healthier Baltimore, we need to look where people are already doing just that."
Daley has long been known as a leader on the issue. His administration was among the first to focus on so-called gateway projects, such as planting flowers in high-traffic medians.
Downtown Chicago's Millennium Park was a major accomplishment of his tenure.
Dixon has similarly focused on "cleaner and greener" initiatives, launching the city's single-stream recycling this year and pushing for more efficient trash collection.