520 S 43rd St, Boulder, CO 80305 Property Records

Boulder County property record for 520 S 43rd St, Boulder, CO 80305

Property Summary

Property Type	Single Family Home
Details	4 bd · 2.25 ba · 2,114 sqft · built 1959
Lot Size	0.166 acres (7,250 sqft)
Owner	2 Individual Names on Record
Last Sale	$395,000 (Apr 2008)
Tax Bill	$4,944 (2025)
Deeds & Mortgages	Feb 2023 Line of Credit May 2020 Mortgage + 1 more
Flood Zone	Zone X (minimal risk)
APN	`1577-08-1-04-002`

Property Details

APN / Parcel Number

Primary APN	`1577-08-1-04-002`
Alternative APNs	`R0009535` `0009535`

Interior

Bedrooms	4 Beds
Full Baths	2.25 Baths
Half Baths	2 Half Baths
Total Rooms	8 Rooms
Stories	1 Story
Building Area	2,114 sqft Living Area
Gross Area	2,478 sqft
1st Floor Area	1,107 sqft
Basement Area	1,107 sqft
Finished Basement	1,007 sqft
Unfinished Basement	100 sqft
Interior Walls	Wallboard/Drywall

Exterior

Year Built	Built 1959
Effective Year Built	Effective 1970
Architectural Style	Ranch
Exterior Material	Brick Veneer
Construction Type	Masonry / Concrete Block
Roof Material	Asphalt
Lot Area	7,250 sqft (0.166 acres)
Garage Type	Attached
Garage Area	264 sqft
Parking Spaces	1 Parking Space
Porch	Porch
Porch Area	300 sqft

Utilities, Heating & Cooling

Cooling System	Evaporative
Heating System	Forced Air with A/C

Location & Zoning

Account Number	R0009535
Street Address	520 S 43RD ST
City	BOULDER
State	CO
Zip	80305-6010
Property Category	Residential
Property Type	Residential > Single Family > Home
Legal Description	LOT 2 BLK 4 MARTIN ACRES 3
Legal Range	70
Legal Township	1S
Legal Section	05
Legal Subdivision	MARTIN ACRES 3 - BO
Legal Block	4
Legal Lot Number	2
Jurisdiction	BOULDER CO
Township / Civil Division	BOULDER
Census Block Group	3
Census Block	3002
Census Tract	12508

Owner

Source: Boulder County records, as of September 18, 2026

Owner names and exact recorded amounts shown locked on this page are available instantly with a free trial.

Owner of Record	2 Individual Names on Record
Mailing Address	520 S 43RD ST, BOULDER, CO 80305-6010
Occupancy	Owner Occupied
Owner Type	Individual

Deeds, Mortgages & Sale History

Date	Document
Feb 9, 2023	Deed of Trust, Mortgage · Line of Credit FIRSTBANK
May 15, 2020	Deed of Trust, Mortgage · Conventional Mortgage QUICKEN LNS
May 5, 2017	Deed of Trust, Mortgage · Conventional Mortgage QUICKEN LNS

Assessor's Deed Record

Deed Names	2 Names on Deed
Last Sale	Apr 28, 2008 · Amount on Record
Deed Sale	Apr 28, 2008 · Amount on Record
Prior Sale	Jun 18, 2007 · Amount on Record
Deed Document Number	20082926166
Record Updated	Oct 29, 2026

February 2023: Deed of Trust, Mortgage

Document Type	Deed of Trust
Jurisdiction	BOULDER CO
Property Address	520 S 43RD ST, BOULDER, CO 80305-6010
Transaction Type	Mortgage
Record Updated	Feb 15, 2023

Transferred To (Grantee/Buyer)

Name	Verified Name
Address	520 S 43RD ST, BOULDER, CO 80305-6010

Mortgage

Document Number	0003996933
Date	Feb 9, 2023
Instrument	3996933

Lender

Name	FIRSTBANK
Type	Bank
Address	DENVER, CO 80215

Agreement

Type	Line of Credit
Amount	Amount Recorded
Term	120 Months
Due	Jan 31, 2033

Interest

Rate Type	Adjustable Rate
Rate	7.5%
Change Frequency	Monthly

May 2020: Deed of Trust, Mortgage

Document Type	Deed of Trust
Jurisdiction	BOULDER CO
Property Address	520 S 43RD ST, BOULDER, CO 80305-6010
Document Number	0003785422
Instrument Date	May 15, 2020
Transaction Type	Mortgage
Record Updated	Jul 14, 2020
Title Company	OTHER

Transferred To (Grantee/Buyer)

Name	Verified Name
Relationship	Husband and Wife
Address	520 S 43RD ST BOULDER CO 803056010, BOULDER, CO 80305-6010

Mortgage

Document Number	0003785422
Date	May 20, 2020
Instrument	3785422

Lender

Name	QUICKEN LNS
Type	Funding / Finance Company
Address	DETROIT, MI 48226-1906

Agreement

Type	Conventional Mortgage
Amount	Amount Recorded
Term	360 Months
Due	May 19, 2050

May 2017: Deed of Trust, Mortgage

Document Type	Deed of Trust
Jurisdiction	BOULDER CO
Property Address	520 S 43RD ST, BOULDER, CO 80305-6010
Document Number	0003591590
Instrument Date	May 5, 2017
Transaction Type	Mortgage
Record Updated	May 26, 2017
Title Company	OTHER

Transferred To (Grantee/Buyer)

Name	Verified Name
Relationship	Husband and Wife
Address	520 S 43RD ST BOULDER CO 803056010, BOULDER, CO 80305-6010

Mortgage

Document Number	0003591590
Date	May 11, 2017
Instrument	3591590

Lender

Name	QUICKEN LNS
Type	Funding / Finance Company
Address	DETROIT, MI 48226-1906

Agreement

Type	Conventional Mortgage
Amount	Amount Recorded
Term	360 Months
Due	May 10, 2047

Tax Assessment & Valuation

Source: Boulder County assessment roll, as of September 18, 2026

Property Jurisdictions

Type	Name
State	Colorado
County	Boulder County
Municipality	Boulder City
Unified School District	Boulder Valley School District RE-2 (PK - 12)

Tax Bill & Assessment History

Year	Tax Bill	Assessed Value	Assessed Market Value
2026		$51,660 (-0.38%) Land $27,806 Building $23,854	$829,700 (-) Land $478,900 Building $350,800
2025	$4,944.00 (+1.79%)	$51,856 (-13.47%) Land $29,931 Building $21,925	$829,700 (-7.24%) Land $478,900 Building $350,800
2023	$4,857.00 (+12.74%)	$59,931 (+29.16%) Land $35,369 Building $24,562	$894,500 (+33.99%) Land $527,900 Building $366,600
2022	$4,308.00	$46,399 Land $26,334 Building $20,065	$667,600 Land $378,900 Building $288,700

Assessed value and assessed market value are set for property tax purposes, not market price estimates; both are a fraction of this property's market value.

Flood

Source: FEMA National Flood Hazard Layer, effective October 14, 2026 · OpenFEMA NFIP redacted claims and policies, as of September 2026

FEMA Flood Zone	Zone X minimal risk
Flood Insurance Requirement	Not required lenders may require it
Community Rating System	Class 5 (25% premium discount)
Nearby Flood Policies	5 in force

Values are read at the parcel center point; flood claims are located to the census block group, not this parcel; lenders make the official flood determination.

Wildfire

Source: USDA Forest Service Wildfire Risk to Communities (2nd edition), as of 2024

Wildfire Risk	Low lower than 67% of the US · lower than 84% of Colorado
Wildfire Likelihood	0.04% annual chance
Exposure	Indirect within ember reach

Values cover an area roughly 900 ft across, not the parcel itself; insurers use their own ratings.

Drinking Water

Source: EPA Safe Drinking Water Information System, as of September 2026

Water System	CITY OF BOULDER serves 166,080 people · EPA ID CO0107152
Water Source	Surface water
Last State Inspection	Sep 2024
Lead	2 ppb (2023–2025) action level 15 ppb

Violations Reported to EPA

Water Quality	Haloacetic acids resolved · Jul 2017
Treatment and Procedure	None last 10 years
Monitoring and Reporting	1 last 3 years

Results are for the whole water system, not water tested at this address; lead at the tap also depends on the building's own pipes.

Internet Providers

Source: FCC Broadband Data Collection, based on 678 locations within half a mile, as of December 31, 2025

Provider	Max Down / Up (Mbps)
Ayva Networks Fixed Wireless	2,500 / 2,500
CenturyLink Fiber · DSL in parts of the area	2,000 / 1,000
Xfinity Cable	2,000 / 250
Verizon Fixed Wireless	300 / 20
LiveWireNet Fixed Wireless	250 / 100
T-Mobile Fixed Wireless	100 / 20

May also be available: AT&T.

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