Federal minimum wage now stands at $7.25 per hour — meaning that non-exempt employees (i.e. those entitled to overtime) must generally receive an hourly wage that is equivalent to or greater than $7.25. Pretty simple — unless you happen to work or own a business in a jurisdiction with a minimum wage that is greater than the federal minimum wage.
Maryland happens to be one of these jurisdictions. Effective January 1, 2015, the minimum wage in Maryland (Labor and Employment Article, Title 3, Subtitle 4, Annotated Code of Maryland) is $8.00 per hour. This summer (on July 1, 2015), the minimum wage in Maryland will increase to $8.25 per hour — $1.00 greater than the federal minimum wage.
To make matters even more confusing for employers (and employees), Montgomery County has its own minimum wage law. As of October 1, 2014, the minimum wage for employees who work in Montgomery County is $8.40 per hour, which will increase to $9.55 per hour on October 1, 2015. By July 1, 2017, the minimum wage in Montgomery County will be $11.50 per hour. A chart summarizing the law can be found here. PG County has a similar law summarized here.
Employers in Maryland outside of Montgomery and PG County must pay employees the higher Maryland minimum wage. Employers in Montgomery and Prince George's counties must pay the even higher minimum hourly wage established by the county.