21 of best ASCs in the country's 5 biggest cities

Nine ASCs in New York City, the country's largest city, and eight ASCs in Houston, the country's fourth largest city, made Newsweek's "America's Best Ambulatory Surgery Centers," which ranks 510 of the more than 5,000 Medicare-certified ASCs in the country.

The ranking, created through a partnership with global research firm Statista, includes ASCs in the 25 states with the most facilities, according to CMS data, by individual state and groups facilities in the remaining states into four regions: Northeast, Midwest, West and South. The rankings are based on recommendations by medical professionals and an analysis of the ASCs' performance data. 

Here are the best ASCs in the five largest U.S. cities, per Newsweek:

New York City:

1. Gramercy Surgery Center
2. Gramercy Surgery Center-Queens
3. East Side Endoscopy
4. Carnegie Hill Endoscopy
5. Manhattan Surgery Center
6. Manhattan Endoscopy
7. Brooklyn Surgery Center
8. Advanced Endoscopy Center-Bronx
9. NYU Langone Health, Outpatient Surgery Center

Los Angeles:

1. UCLA Health, Ambulatory Surgery Center Westwood

Chicago:

1. Rush SurgiCenter

Houston:

1. HCA Healthcare, Gramercy Outpatient Surgery Center
2. United Surgical Partners International, Memorial Hermann, Surgery Center Texas Medical Center
3. USPI, Memorial Hermann, Surgery Center Kirby Glen
4. USPI, Texas International Endoscopy Center
5. USPI, Memorial Hermann-North Houston Endoscopy & Surgery Center
6. Museum District Aesthetic Surgery Center
7. Physicians Ambulatory Surgery Center
8. Memorial Hermann, Surgery Center Southwest

Phoenix

1. Dignity Health, St. Joseph's Outpatient Surgery Center
2. Banner Health, Banner Surgery Center-University