This is a counties and county-equivalents in the U.S. state of Maryland. Though an independent city rather than a county, the City of Baltimore is considered the equal of a county for most purposes and is a county-equivalent. Many of the counties in Maryland were named for relatives of the Barons Baltimore who were the proprietors of the Maryland colony from its founding in 1634 through 1771. The Barons Baltimore were Catholic, and George Calvert, 1st Baron Baltimore, originally intended that the colony be a haven for English Catholics, though for the majority of its history Maryland has had a majority of Protestants.
The last new county formation in Maryland occurred when Garrett County was formed in 1872 from portions of Allegany County. However, there have been numerous border changes since that time, most recently when portions of the city of Takoma Park that had previously been part of Prince George's County were absorbed into Montgomery County in 1997.
Outside of Baltimore (which is an independent city) the county is the default unit of local government. Under Maryland law, counties exercise powers reserved in most other states at the municipal or state levels, so there is little incentive for a community to incorporate. Many of the state's most populous and economically important communities, such as Bethesda and Silver Spring, are unincorporated and receive their municipal services from the county. In fact, there are no incorporated municipalities at all in either Baltimore County or Howard County. The county-equivalent is also the provider of public schools - School districts as a separate level of government do not exist in Maryland.