Stephen Tilly, principal of the firm, graduated from M.I.T. with a Master of Architecture, following a BA (English Literature) from Grinnell College. After hands-on work as a general contractor, he did research, planning and urban design in Boston, Washington and New York. He became a partner in Design Coalition, an adventurous design firm that helped pioneer New York's historic Soho district in the 1970s and 1980s. With Elizabeth Martin, Mr. Tilly founded a mission-based studio in Dobbs Ferry focused on delivering high end design, especially targeting socially useful projects. The work since reflects a broad range of interests including affordable housing, historic preservation, low-impact environmental design and community planning. Frequent pro bono and grant-funded projects have made him familiar with the dynamics of non-profits. He has served on local land use committees and boards and is the Chair of the Advisory Board of the National Trust for Historic Preservationís Lyndhurst Historic Site. For the National Trust for Historic Preservation and the Association for Preservation Technology, he has spoken and written on the essential connection between preservation and sustainability.