South Station to Union Square, Somerville
How to get from South Station to Union Square, Somerville on public transit, with the stops, times and the last trip of the night.
South Station to Union Square, Somerville
- Red Line
- Bus 109
- Take the Red LineFrom South Station, toward Alewife6 stops, about 13 min
- Change at Harvard
- Take bus 109Toward Linden Square via Sullivan6 stops, about 11 min
- Get off at Somerville Ave @ Union SqThe stop after Washington St opp Hawkins St
Weekdays, fall 2026 schedule · First and last trips
Quick answer: Take the Red Line toward Alewife to Harvard, then bus 109 to Somerville Ave @ Union Sq. The trip takes about 35 minutes (32-39 min depending on the connection). On weekdays bus 109 runs every 12 min during the day.
Get the live route from South Station to Union Square
Step by step
- At South Station, take the Red Line toward Alewife.
- Ride 6 stops, about 13 min, through Downtown Crossing, Park Street, Charles/MGH, Kendall/MIT and Central, and get off at Harvard.
- At Harvard, change to bus 109 toward Linden Square via Sullivan.
- Ride 6 stops, about 11 min. Get off at Somerville Ave @ Union Sq, the stop after Washington St opp Hawkins St.
Other ways to go
- Take the Red Line toward Alewife to Park Street, then the Green Line to Union Square, and walk about 7 min: about 37 min.
- Take the Red Line toward Alewife to Kendall/MIT, then bus 85 to Prospect St @ Union Sq - Green Line, and walk about 5 min: about 30 min.
Which one is faster depends on when you leave. Cobblehop compares them with live times and gives you the one that gets you there first.
Times and frequency
| Day | First trip | Last trip | How often (daytime) | Trip time |
|---|---|---|---|---|
| Monday-Thursday | 4:31 am | 1:03 am | Every 12 min | About 35 min |
| Friday | 4:31 am | 1:43 am | Every 12 min | About 35 min |
| Saturday | 5:30 am | 1:44 am | About every 15 min | About 34 min |
| Sunday | 6:15 am | 12:45 am | About every 15 min | About 34 min |
First and last trip are when the first train of the trip leaves South Station, on the fall 2026 schedule. "How often" is for bus 109 (the least frequent part of the trip).
Late at night
On weekdays, the last trip that works leaves South Station at 1:03 am and gets to Union Square, Somerville around 1:30 am, using Green Line and bus 109. On Friday nights it runs later: the last trip leaves at 1:43 am. On Saturday nights the last trip leaves at 1:44 am, and on Sunday nights at 12:45 am. Late at night, ask Cobblehop for the last trip. It checks live times and tells you when to leave.
Tips for this trip
- Know your stop. Get to the door after Washington St opp Hawkins St. The next stop is Somerville Ave @ Union Sq. Start a live trip in Cobblehop and it alerts you before your stop.
- Changing at Harvard. You don't leave the station. Follow the signs for bus 109.
- Union Square station is the end of the Green Line D branch, a short walk from the square.
- South Station has the Red Line and Silver Line underground, Commuter Rail and Amtrak on the main concourse, and the intercity bus terminal upstairs next door.
Step-free access
MBTA data lists every station on this route (South Station and Harvard) as accessible. South Station has 9 elevators in MBTA data. Elevators do break, so check the MBTA's elevator alerts before you go.
What it costs
- Subway and bus. The subway is $2.40 one way, and a local bus is $1.70. Under an MBTA pilot that started September 1, 2026, you can change between bus and subway within 2 hours of your first tap and pay only the highest fare, if you use the same card or phone each time.
- How to pay. Tap a contactless credit or debit card, phone or watch at the fare gate or bus door, or use a CharlieCard or CharlieTicket.
- Kids. Children 11 and under ride the MBTA free.
Fares as of October 2026. Check the MBTA's fares page before you ride.
South Station to Union Square, Somerville: common questions
How do I get from South Station to Union Square, Somerville by public transit?
Take the Red Line toward Alewife to Harvard, then bus 109 to Somerville Ave @ Union Sq. The trip takes about 35 minutes (32-39 min depending on the connection).
How long does it take to get from South Station to Union Square, Somerville?
About 35 minutes on the main route, or 32-39 minutes depending on the connection.
Do I have to change along the way?
Yes, once: at Harvard. Take the Red Line toward Alewife to Harvard, then bus 109 to Somerville Ave @ Union Sq.
How often does bus 109 run?
Every 12 min on weekdays during the day, about every 15 min on Saturdays and about every 15 min on Sundays, on the fall 2026 schedule.
What time is the last train from South Station to Union Square, Somerville?
On weekdays, the last trip that works leaves South Station at 1:03 am and gets to Union Square, Somerville around 1:30 am, using Green Line and bus 109. On Friday nights it runs later: the last trip leaves at 1:43 am. On Saturday nights the last trip leaves at 1:44 am, and on Sunday nights at 12:45 am.
Related routes
- South Station to Inman Square
- South Station to Cambridge Hospital
- Boston Common to Union Square, Somerville
- North Station to Union Square, Somerville
- Never miss your stop (guide)
More routes from South Station
- South Station to Central Square, Cambridge
- South Station to Harvard Art Museums
- South Station to Harvard Museum of Natural History
- South Station to MIT Museum
- South Station to MIT
- All routes from South Station
Official sources
Cobblehop is independent and isn't affiliated with these agencies or operators. Schedules on this page come from MBTA/MassDOT public data. Check their pages for the latest schedules and service changes:
- MBTA: Red Line
- MBTA: bus 109
- MBTA: South Station station
- MBTA: Harvard station
- MBTA: fares
- MBTA: elevator and accessibility alerts
Published October 30, 2026. Times were computed from the fall 2026 MBTA schedule (2026-11-04 for weekdays). Service changes, so check Cobblehop for live times before you go.
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