1355 Market Street, Suite 900, San Francisco, CA 94103 is the high-profile business address for the headquarters of X Corp. (formerly known as Twitter, Inc.). Located within the historic Market Square building in the city’s Mid-Market district, Suite 900 served for over a decade as the primary reception point and corporate face of one of the world’s most influential social media platforms.
The significance of this specific address extends far beyond a simple office suite. It represents a pivotal chapter in San Francisco’s urban development, the rise of the "Web 2.0" era, and the subsequent radical transformation of the tech industry under the leadership of Elon Musk. As of 2026, the address remains a landmark of Silicon Valley’s physical footprint in San Francisco, even as the company's operational center of gravity has shifted toward Texas.
The Architecture and History of Market Square
1355 Market Street is more than just a tech hub; it is an architectural icon known as Market Square. Originally constructed in 1937, the building was designed by the renowned architectural firm Schultze and Weaver—the same firm responsible for the Waldorf-Astoria in New York.
For decades, the structure served as the Western Furniture Exchange and Merchandise Mart. It was a massive wholesale center where retailers from across the western United States came to view the latest in home furnishings and appliances. The building’s Art Deco facade, characterized by its verticality and intricate stonework, remains a testament to the pre-war industrial optimism of San Francisco.
The Mid-Market Revitalization
By the early 2000s, the building and the surrounding Mid-Market area had fallen into significant disrepair. The neighborhood was plagued by high vacancy rates and economic stagnation. In 2011, Shorenstein Properties acquired the building and began a massive $300 million renovation to convert the furniture mart into a "Class A" creative office space.
This renovation was the catalyst for what became known as the "Twitter Tax Break" (the Mid-Market Central Business District Community Benefit Agreement). To incentivize tech companies to stay in San Francisco rather than moving to the Peninsula or South Bay, the city offered a payroll tax exemption on new hires for companies located in this specific zone. Twitter’s move to 1355 Market Street in 2012 was the centerpiece of this economic experiment.
Inside Suite 900: The Corporate Heart of X
While the company eventually occupied several floors within the 1355 Market Street complex (and the adjacent 1 Tenth Street building), Suite 900 was historically the "front door."
The Reception Experience
For years, visitors, job candidates, and dignitaries arriving at Twitter began their journey in the Suite 900 lobby. The interior design of the 9th floor was famous for its "urban lodge" aesthetic. It featured reclaimed wood from 19th-century barns, sleek modern lines, and the iconic "Twitter bird" logo, which has since been replaced by the minimalist "X" branding.
The suite was designed to facilitate a blend of high-security corporate operations and the open-concept culture typical of San Francisco startups. It housed executive offices, key administrative functions, and the primary check-in kiosks for the entire campus.
Technical Infrastructure
The 9th floor and the building at large were outfitted with state-of-the-art fiber optics and redundant power systems to support the massive data requirements of a global social network. The conversion from a 1930s furniture mart to a 21st-century server-ready facility required significant structural reinforcement and the installation of modern HVAC systems to cool the dense clusters of hardware and personnel.
The 2024-2026 Transition: From San Francisco to Texas
In late 2022, following the acquisition of Twitter by Elon Musk, the nature of the 1355 Market Street headquarters underwent a fundamental shift. By mid-2024, Musk announced that X Corp. would officially move its headquarters to Austin and Bastrop, Texas, citing concerns over San Francisco’s regulatory environment and local safety issues.
Current Status in 2026
As of 2026, the status of Suite 900 is that of a legacy corporate hub. While the official legal headquarters of X Corp. has transitioned to the Texas corridor, the company maintains a physical presence in San Francisco, though it is significantly scaled back from its 2019 peak.
Many of the floors previously occupied by the company have been returned to the landlord, Shorenstein Properties, or have been listed for sublease. However, Suite 900 remains a focal point for the remaining engineering and core infrastructure teams that have chosen to stay in the Bay Area to tap into the local AI and software talent pool.
Real Estate Impact
The partial vacancy of 1355 Market Street has had a profound impact on the San Francisco commercial real estate market.
- Office Vacancy: The "X-exit" contributed to the city's record-high office vacancy rates seen in the mid-2020s.
- Adaptive Reuse: There has been ongoing discussion in 2025 and 2026 regarding converting parts of the Market Square complex into residential units or life-science labs, though the building’s layout remains most conducive to tech office use.
Logistics and Access for Visitors
If you have a scheduled business meeting or need to visit 1355 Market Street, understanding the logistics of the Mid-Market area is essential.
Transportation and Parking
The building is located at the intersection of Market Street and 9th Street, making it one of the most accessible locations in the city via public transit.
| Transport Mode | Station/Location | Distance |
|---|---|---|
| BART | Civic Center/UN Plaza | 1 Block |
| MUNI Metro | Civic Center Station | 1 Block |
| MUNI Bus | Lines 5, 6, 7, 9, 21 | Multiple stops within 500 feet |
| Parking | 1355 Market Garage | On-site (expensive) |
| Bicycle | Secure Bike Room | Basement access for employees |
Security Protocols
Security at 1355 Market Street is stringent. Visitors cannot simply walk up to Suite 900.
- Check-in: Visitors must check in at the main ground-floor security desk in the lobby of 1355 Market Street.
- Identification: A valid government-issued photo ID is required.
- Escort: Once cleared by the ground floor, visitors are typically met by an employee or directed to the 9th-floor elevators, where a secondary reception check-in occurs.
The Cultural Significance of the Address
The address 1355 Market Street, Suite 900, is etched into the history of the "Tech Boom 2.0." It was here that the "Hashtag" was popularized, where global movements like the Arab Spring were documented in real-time, and where the transition from a public company to a private entity under Elon Musk took place.
The "X" Sign Controversy
In 2023, the building became a flashpoint for local controversy when a giant, pulsing, illuminated "X" sign was briefly installed on the roof of 1355 Market Street without proper permits. The sign was removed shortly after following complaints from neighbors and building inspectors, but the incident solidified the address as a symbol of the friction between "move fast and break things" tech culture and municipal governance.
Surrounding Amenities
For those visiting the suite, the building itself offers several high-end amenities:
- The Market: A luxury grocery store and food hall located on the ground floor, offering everything from sushi to wood-fired pizza.
- Fitness Centers: The building houses premium gym facilities used by the various tech tenants.
- Roof Deck: Market Square features one of the largest private roof decks in the city, offering panoramic views of the San Francisco skyline and City Hall.
Common Questions Regarding 1355 Market St Suite 900
Is X (Twitter) still located at 1355 Market Street?
Yes, but in a reduced capacity. While the official corporate headquarters moved to Texas in late 2024, X Corp. still holds a lease and maintains a presence at the 1355 Market Street address as of 2026. Suite 900 remains the primary point of contact for their San Francisco operations.
Can I visit the 9th floor without an appointment?
No. 1355 Market Street is a private office building with high-level security. There are no public tours of Suite 900 or the X offices. Public access is limited to the ground-floor retail spaces, such as The Market.
What happened to the rent dispute between X and the landlord?
In 2023 and 2024, there were multiple reports of rent disputes and lawsuits involving X Corp. and Shorenstein Properties. Most of these legal challenges were settled or moved to arbitration as part of the company's restructuring and partial relocation. By 2026, the company has stabilized its footprint within the building.
Who else is in the building at 1355 Market Street?
Beyond X Corp., the building has hosted various other tech tenants over the years, including companies like Block (formerly Square), though many have shifted toward hybrid or remote work models. The ground floor remains occupied by retail and dining establishments that serve the local tech workforce.
What is the zip code for 1355 Market Street?
The zip code is 94103. This area covers the South of Market (SoMa) and Mid-Market districts of San Francisco.
Practical Recommendations for Business Visitors
If you are traveling to 1355 Market Street, Suite 900 for professional reasons in 2026, keep the following tips in mind:
- Confirm the Location: Given X Corp.'s dual presence in California and Texas, ensure your meeting is specifically at the San Francisco office and not the Austin headquarters.
- Allow Extra Time for Security: The check-in process at the ground floor can take 10–15 minutes during peak hours (9:00 AM – 10:30 AM).
- Use Public Transit: Parking in the Mid-Market area is both scarce and expensive. The proximity to the Civic Center BART/MUNI station makes public transit the most efficient way to arrive.
- Local Safety Awareness: While the building itself is highly secure, the Mid-Market neighborhood has faced challenges with street safety and cleanliness. It is advisable to remain aware of your surroundings when walking to and from the building.
- Digital Credentials: Ensure you have any required digital visitor passes or QR codes ready on your mobile device, as the building utilizes modern access control systems.
1355 Market Street, Suite 900, remains a monument to the volatility and vibrancy of the technology sector. Whether viewed as a symbol of San Francisco's resilience or a reminder of the shifting tides of corporate headquarters, it remains one of the most famous addresses in the global tech landscape.
