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CondominiumResidential
$709,474$994 / ft²
TopHap EstimateOur estimate of what this home would sell for today, based on nearby sales, the home's size and features, and local price trends. It is a starting point, not an appraisal.· confidence 92How well the pricing models agreed with each other on this home. Higher means the estimate rests on stronger, more consistent data.· as of Sep 24, 2026
Last sold for $725,000 on Aug 9, 2021

23 UNION ST

CHARLESTOWN, MA 02129
Building report
2
Beds
1
Baths
714 ft²
Living AreaTotal finished area of the structures, from county records. Some counties include shared space like hallways or a building gym, so it may not match a listing.
714 ft²
Lot SizeThe size of the land the home sits on, from county records.
1870
Year BuiltThe year the home was originally built, according to county records.
1
StoriesHow many floors the home has above ground.
4
RoomsThe total room count in county records. Counties differ on which rooms they count, so compare it loosely.
1
ParkingThe number of parking spaces on the property, including the garage.

Valuation

$709K
$652K low$767K high
Last SaleThe most recent sale price and date from the recorded deed. Transfers between family members or companies may not reflect market value.$725,000 · Aug 9, 2021

Tax & Assessment

Property TaxThe property tax billed for this tax year. It usually pays for schools, roads, and local services.$7,088 (2025)
Assessed ValueThe value the county assigns to this home to calculate property tax. It is often lower than what the home would sell for.$612,100 (2025)
Assessed ImprovementsThe share of the county's assessed value that comes from the buildings and other structures on the land.$612,100
Assessor Market ValueThe county assessor's own opinion of market value. It is separate from our estimate and updates on the county's schedule.$912,570

Property Facts

Property TypeThe broad category the county puts this property in, such as residential or commercial.Condominium
CountySUFFOLK
Effective Year BuiltAn adjusted build year that accounts for condition and major remodels. A big renovation can make a home count as newer than it is.1991
Lot (acres)The size of the land the home sits on, from county records.0.02
HeatingThe type of heating system in the home.Hot Water
PoolWhether the property has a pool, and what kind, such as in-ground.No
FeaturesExtra features found in county records. Records are not complete everywhere, so a missing feature does not always mean the home lacks it.Deck

Transaction History(8)

Sales and refinances filed with the county for this home. Not every transfer is a normal sale, so check the type before comparing prices.

Assigned SchoolsThe public schools this address is zoned for. Boundaries change, so confirm with the district before you count on it.

E
Warren / Prescott K-8 SchoolA-
Elementary · Grades PK–8 · 0.3 mi
H
Horace Mann School For The Deaf
High · Grades PK–12 · 0.4 mi

District: Boston School District

Neighborhood · ZIP 02129These are comparison scores, not percentages. 100 equals the national average, so 150 means about 50% above average.

CrimeLocal crime compared with the rest of the country, where 100 is average. It reflects things like population density, income, and how crime gets reported.89
Air pollutionOverall air pollution compared with the rest of the country, where 100 is average. Lower is cleaner.101
EarthquakeEarthquake risk and likely building damage compared with the rest of the country, where 100 is average. Scores can run far above 100.73

Index scale: 100 = US average (tick). Lower is better.

Homes occupiedThe share of homes here that someone lives in. The rest sit empty, including vacation and for-sale homes.94%
Bachelor's or higherThe share of adults 25 and older whose highest degree is a bachelor's degree.35%
Poverty rateThe share of people whose household income falls below the federal poverty line, which varies by family size.8.3%
UnemploymentThe share of men 16 and older who are out of work and actively looking. Only men are counted in this figure.1.3%
PopulationHow many people live in this area.18,397
DensityPeople per square mile. Higher numbers mean a more crowded, urban area.10,594 / mi²
Median incomeThe middle household income here — half of households earn more, half earn less.$152,177
Average incomeThe average household income. It runs higher than the median when a few high earners pull it up.$178,903
Average tempThe average temperature here across a full year.50°F
Annual precipHow much rain and melted snow falls here in a typical year.46 in
SunshineThe share of daylight hours that get direct sun in a typical year, counting cloud cover.58%

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Data by ATTOM. Valuations are automated estimates, not appraisals. Photos from Google Street View and may not depict the current property state.

How this home compares

23 Union St measured against every home in its neighborhood, its ZIP code and its county, using county assessor records refreshed nightly. A home can stand out in one of those areas and look ordinary in another, because each one holds a different mix of homes.

  • Worth less than 78% of homes in Charlestown 02129
  • Costs more per square foot than 78% of homes in Suffolk County
  • Smaller than 88% of homes in Suffolk County
  • Has a smaller lot than 88% of homes in Suffolk County
  • Older than 97% of homes in Suffolk County

What homes are worth in Charlestown 02129

Each bar is how many homes fall in that price range. The marker is this home.

This home
$457K$3M

This home is worth more than 22% of homes in Charlestown 02129.

How it measures up in Charlestown 02129

The dot is this home. The mark in the middle is the typical home in Charlestown 02129.

Estimated value$709,474
CheaperTypical $1,040,289Pricier

Pricier than 22% of homes nearby

Price per ft²$994
CheaperTypical $943Pricier

Pricier than 63% of homes nearby

Living area714 ft²
SmallerTypical 1,204 ft²Bigger

Bigger than 15% of homes nearby

Lot size714 ft²
SmallerTypical 1,089 ft²Bigger

Bigger than 16% of homes nearby

Year built1870
OlderTypical 1899Newer

Newer than 18% of homes nearby

How 23 Union St ranks against every home in each area.
MeasureThis homeCharlestown 02129Suffolk County
Estimated valuepricier than$709,47422% of homes50% of homes
Price per ft²pricier than$99463% of homes78% of homes
Living areabigger than714 ft²15% of homes12% of homes
Lot sizebigger than714 ft²16% of homes12% of homes
Year builtnewer than187018% of homes3% of homes

About 23 Union St

How much is 23 Union St, Charlestown, MA worth?

The TopHap Estimate for 23 Union St, Charlestown, MA is $709,474 as of Sep 24, 2026. The likely range is $652,203 to $766,745. The estimate is modelled from recorded sales, assessments and the property's own characteristics — it is not an appraisal.

When did 23 Union St, Charlestown, MA last sell?

23 Union St, Charlestown, MA last sold on Aug 9, 2021 for $725,000, according to the county's recorded deed. TopHap holds 5 recorded sales for this parcel.

How big is 23 Union St, Charlestown, MA?

23 Union St, Charlestown, MA has 2 bedrooms, 1 bathrooms, 714 square feet of living space and a 0.02-acre lot.

When was 23 Union St, Charlestown, MA built?

23 Union St, Charlestown, MA was built in 1870, making it 156 years old. The building has 1 story.

What schools serve 23 Union St, Charlestown, MA?

23 Union St, Charlestown, MA is assigned to Warren / Prescott K-8 School (elementary), rated A-; Horace Mann School For The Deaf (high). All sit in Boston School District. Attendance boundaries change — confirm with the district before relying on an assignment.

How does 23 Union St, Charlestown, MA compare to other homes in Charlestown 02129?

Among the 5,261 homes in Charlestown 02129, it is worth more than 22% of them ($709,474 against a typical $1,040,289), its price per square foot is higher than 63% of them ($994 against a typical $943), it is bigger than 15% of them (714 ft² against a typical 1,204 ft²), its lot is bigger than 16% of them (714 ft² against a typical 1,089 ft²) and it is newer than 18% of them (1870 against a typical 1899). Measured against all of Suffolk County, it is worth more than 50% of homes there. These shares are recounted nightly from the full county assessor record for each area, not from active listings.

What are the property taxes on 23 Union St, Charlestown, MA?

The 2025 property tax bill for 23 Union St, Charlestown, MA was $7,088. The county assessed it at $612,100.

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