Baltimore County (MD) Building & Trade Permits

Who pulled a permit for what, where, in Baltimore County, Maryland - the building / construction, electrical, gas and plumbing permit registers in one query API.

Data

Four county permit registers (public government open data) unified under one schema - ~310,000 permits:

Register	Records	What it holds
building	~165,000	building & construction permits - new dwellings, alteration/addition, decks, fences, sprinklers, accessory structures, commercial work. The deep register: owner, estimated cost, assessor parcel, existing/proposed use, district, full work description
electrical	~64,000	electrical permits (residential + commercial)
gas	~42,000	gas permits
plumbing	~39,000	plumbing permits

Every permit carries the owner, the issued / applied / occupancy dates, the permit type and subtype, and the full scope-of-work text. Street address is published on essentially every building permit and on roughly half of the trade registers; the assessor parcel is on the building register. Work dates run current - the register is live to this week.

Low cost

From $0.0003 per record.

Digging county permit records usually means trading between four separate registers that disagree with each other. The building layer speaks a different status vocabulary than the trade layers (ISSUE / CANCELLED there, ISSUED / CANCEL here), costs only exist on the building register, and each layer's ~65-column depth is mostly empty scaffolding. We normalized all four onto one schema with per-register status matching, real date parsing, and empty-field handling - so permitNumber / owner / status / workDescription / address / district / zip / date-window filters just work, and aggregates by type / status / subtype / district / land use come back clean. You query one clean register; the archaeology stays with us.

Every record is one flat JSON object - no HTML, no pagination to chase, no shape-shifting between registers.

Use cases

• Construction & trade leads - find permits by type, district, or date window; track new dwelling construction in a council district
• Diligence - check whether a property or owner has active or recent permits, by address, owner, or exact permit number
• Market analysis - aggregate what kind of work is being pulled, where, over time

Inputs

Field	What it does
source	building / electrical / gas / plumbing register
permitNumber	exact permit lookup (e.g. R26-05266)
owner / address / zip	find permits by property or owner
workDescription	search the scope-of-work text
status	filter by exact status, or issued/open/closed/expired/cancelled/complete
issuedFrom / issuedTo / appliedFrom / appliedTo	date windows
aggregate + groupBy	summary counts by type / status / subtype / district / landUse

Output fields

permitNumber / status / type / subtype / workDescription / ownerName / address / district / zip / estCost / applyDate / issuanceDate / occupancyDate / assessorNumber / proposedUse / existingUse / landUse / totalUnits / floorArea + register depth fields.

Note on honesty: the source publishes the contractor on no register (that column exists but is empty everywhere) - this API does not invent it. Building permits carry estimated cost on ~14% of rows, districts on ~14%; trade permits carry neither. Those fields are returned only where the county actually records them.

Source: Baltimore County government open data (public permit registers).