Park Rx America

Park Rx America (formally DC Park Rx) is a non-profit organization whose mission is to decrease the burden of chronic disease, increase health and happiness, and foster environmental stewardship, by virtue of prescribing Nature during the routine delivery of healthcare.


We work closely with managers of publicly-accessible land and water, as well as directly with healthcare providers and their respective organizations, to "make it easy" to prescribe parks and other protected areas to their patients real-time in the clinical practice setting.

Over 100 million Americans currently suffer from a chronic disease (e.g., coronary heart disease, stroke, high blood pressure, Type 2 diabetes, and mental health conditions). More than two thirds of American adults currently suffer from overweight/obesity, which contributes to chronic disease. Chronic disease results in decreased quality of life, and ultimately, premature death.

Spending time in natural environments increases physical activity, hence decreasing the risk of developing chronic disease. Park Rx America is a low-cost intervention that utilizes a known, generally trusted, and accessible resource - parks - to influence positive health outcomes. To date, Park Rx America has mapped and rated hundreds of parks in the national capital region, and developed Park Pages (one-page park summaries) searchable database, which is now available to you to help you find the best park for you.



Park Rx America Team


Dr. Robert Zarr, MD, MPH, Founder & Medical DirectorDr. Robert Zarr, MD, MPH, Founder & Medical Director

Dr. Robert Zarr is a board-certified pediatrician at Unity Health Care, located in Washington, DC, where he cares for low-income and immigrant populations. He previously served as advisor to the National Park Service on park prescriptions. You will often find him riding his recumbent trike on the Capital Crescent Trail.


John Henderson, Executive DirectorJohn Henderson, Executive Director

John is a Certified Parks and Recreation Executive, city planner, public participation practitioner, arbitrator, and mediator. He is also an attorney licensed to practice law in Illinois and the District of Columbia. He enjoys hiking and biking and is passionate about finding opportunities to bring nature into city neighborhoods.


Matthew Scribner, Chief Technology OfficerMatthew Scribner, Chief Technology Officer

Matthew is a DC native "full-stack" developer with knowledge in both front-end to back-end software development. He believes in coding for a cause and finding ways to make technology easy and accessible.


Nhu Le, Nature Engagement LiaisonNhu Le, Nature Engagement Liaison

Nhu is pursuing her Master of Public Health in Physical Activity in Public Health at The George Washington University this Winter. Nhu is fueled by her passion of connecting like-minded individuals and organizations to health and wellness. During her free time, Nhu loves to travel, spend time outdoors hiking and walking trails, and continue advancing her exercise and yoga practices.

Advisory Board


Peter Harnik

Peter Harnik founded the Trust for Public Land's Center for City Park Excellence and served as its director for almost 20 years... He is author of the books Inside City Parks and Urban Green: Innovative Parks for Resurgent Cities and also of numerous studies and reports on park funding, the economics of parks, park design, park advocacy, and the issue of parks and health.

Before TPL, he co-founded and served as vice president of the Rails-to-Trails Conservancy, the national organization seeking to preserve abandoned railroad corridors for bicycling and walking. Previous to that he was coordinator of Environmental Action, Inc., the group that sponsored Earth Day, 1970. He is also co-founder of City Parks Alliance and was an advisor to the television production, Ten Parks That Changed America.

He is a former president of the Washington Area Bicyclist Association and a co-founder of the Coalition for the Capital Crescent Trail. He is currently writing a history of the rails-to-trails movement.


Terry Horton

Dr. Teresa Horton is an associate professor of research in the department of Anthropology at Northwestern University... Trained as a biologist, she is a member of the Evolutionary and Ecological Approaches to Health and Development (E2HD) research group. Dr. Horton combines the theory and practice of ecology, evolution, neuroendocrinology, and physiology to investigate the mechanisms by which environmental conditions alter physiology and behavior of humans.

Her early research in wild and laboratory animal models was among the first to show that pregnant females transmit environmental information to their fetuses which significantly alters their postnatal development. Subsequent work examined the endocrine mechanisms by which environmental cues influence physiology and behavior. Since joining the Department of Anthropology at Northwestern University she has initiated research projects which investigate the neural, endocrine, and immunological mechanisms by which exposure to natural landscapes can improve human health and well-being.


Rachel Kaul

Rachel Kaul is a clinical social worker who serves as the Deputy Director of Clinical Services for USAID's Office for Staff Care where she oversees clinical services related to promoting employee resilience and wellbeing within the overall context of health and wellness... Previously, Rachel was the Behavioral Health Lead for the Division for At-Risk Individuals, Behavioral Health, and Community Resilience at the Department of Health and Human Services. In this capacity she provided guidance to the disaster mental health community throughout the country in promoting expansion and improvement of behavioral health services to foster individual and community resilience.

She served as a Federal Project Officer responsible for planning, organizing, directing, and evaluating mental health crisis counseling services to survivors of Presidentially-declared disasters.

Rachel provided oversight and guidance for crisis counseling projects for evacuees from Hurricanes Katrina and Rita and has been a responder for community and workplace crisis teams and a disaster mental health responder with the American Red Cross. She was the Coordinator of Crisis Response Services with the Employee Assistance Program at the Pentagon for two years after the 9/11 attack.

Rachel has published articles and book chapters on disaster mental health and emergency response, death notification, stress management and crisis intervention.


Kathleen A. Knolhoff

Kathleen Knolhoff, Chief Executive Officer and President, CCI Health & Wellness Services, has spent more than 25 years in public health... She holds a Bachelor of Science (BS) in Dietetics/Nutrition from the University of West Florida, a Master of Public Health (MPH) from the University of Alabama at Birmingham, a Graduate Certificate in Survey Design and Data Analysis from The George Washington University, Washington, DC, and studied at Johns Hopkins University in Baltimore, MD as part of a Graduate Certificate in Health Finance and Management.

Mrs. Knolhoff became the Chief Executive Officer and President in 2014 after serving for nearly ten years as a member of the senior management team at CCI. Prior to joining CCI in 2009, Ms. Knolhoff worked for nearly a decade at the State of Maryland Department of Health and Mental Hygiene, first as the Health Officer for Talbot County, Maryland and following that as the Director of the Maryland WIC Program.


Dee Merriam

Dee Merriam is a Landscape Architect working on community design issues with a focus on public space and how it promotes public health... She has recently retired from the Centers for Disease Control and Prevention (CDC) National Center for Environmental Health (NCEH) where her program, the Healthy Community Design Initiative, looked at the relationship between community design and public health.

In 2016 she received the NCEH/ATSDR Thomas A. Bartenfeld honor award for excellence in public health practice. She managed park system planning for DeKalb County Georgia for over 20 years.

In 2005 she was asked to lead Project Greenspace for the City of Atlanta where she looked broadly at the need for greenspace as an integral part of the city fabric. Dee is a Fellow in the American Society of Landscape Architects and holds masters degrees in Landscape Architecture, University of Georgia, and in City and Regional Planning, Georgia Institute of Technology.


Ranit Mishori

Dr. Ranit Mishori is a Professor of Family Medicine at Georgetown University School of Medicine... After covering wars and the plight of refugees for a global news organization, Dr. Mishori went on to study medicine and public health, earning an MHS in International Health from Johns Hopkins Bloomberg School of Public Health, and an MD from Georgetown University School of Medicine.

Dr. Mishori's main areas of interest and expertise are health and human rights and the care of vulnerable populations, particularly forced migrants. She is currently director of Global Health Initiatives in the Department of Family Medicine, where she initiated the Global Health Scholars Track and leads various collaborative projects in Latin America, Haiti, Africa and the Middle East.

Dr. Mishori is the founder of the program on Health, Media and Primary Care in the Department of Family Medicine, with a mission to assess the intersection between media, evidence-based medicine and primary care. At Georgetown Ranit directs the Health & Media fellowship and the Practice-Based Research Network, CAPRICORN. She is the recipient of the Leonard Tow Humanism in Medicine Award, John Eisenberg Memorial Career Development Award, the STFM-NE Emerging Leader Award, and The Georgetown University School of Medicine International Programs Award.


Teresa Penbrooke

Dr. Teresa Penbrooke is co-founder of GP RED, a national nonprofit that provides Research, Education, and Development for health, recreation, and land management agencies... She serves as the Director of the Healthy Communities Research Group, focusing on community design and teaching.

Teresa is the CEO and Founder of Green Play, LLC, a leading national private parks, recreation, tourism, and open space consulting firm, which has completed community engagement and planning for over 475 communities since 1999. Teresa is also a Visiting Scholar at North Carolina State University, having received her PhD there in Parks, Recreation, and Tourism Management in 2017 and helping to update planning curriculum in the College of Design. Her academic career started with a BS in Kinesiology and a Masters in Organizational Management.

Teresa authors books and articles, teaches for state and national associations and universities, and consults on operations, management, master planning, and community engagement.


Jennifer Roberts

Dr. Jennifer D. Roberts is an Assistant Professor of Kinesiology at the University of Maryland College Park, School of Public Health... She is also the Director of the Public Health Outcomes and Effects of the Built Environment (PHOEBE) Laboratory. Her research interests focus on the relationship between the built environment and physical activity in addition to its impact on obesity and other public health outcomes.

More specifically, much of her research has explored the dynamic relationship between environmental, social and cultural determinants of physical activity and using empirical evidence of this relationship to infer complex health outcome patterns among adults and children. Studies have incorporated state of the art techniques, such as spatial analysis and geographic information system modeling in order to objectively capture the role and relationship of physical activity determinants.

Dr. Roberts has also been awarded funding from the National Institutes of Health and the National Science foundation as well as professional development awards from the Robert Wood Johnson Foundation.


David Sabgir

Dr. David Sabgir, is a board-certified cardiologist with Clinic Cardiovascular Specialists at Mount Carmel St. Ann's in Westerville, OH... David is the Founding CEO of Walk with a Doc which began in 2005. Walk with a Doc puts doctors in parks across the country and around the world. Walk with a Doc currently has 370 chapters in 46 states and 21 countries. Walk with a Doc has been featured in the Wall Street Journal, JAMA, AARP, Cooking Light, and Medical Economics among others.

David is honored to have been recognized by the American Heart Association, the US Surgeon General, ACSM, and as a 2015 CNN Hero.

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