The Best Capitol Trades APIs for Congressional Stock Data in 2026

Between January and March 2026, our research team conducted a hands-on evaluation of 12 APIs and platforms that provide congressional stock trading data—the disclosure records filed under the STOCK Act by U.S. senators and representatives. We tested each provider against standardized benchmarks covering chamber coverage, data freshness, filtering depth, and developer experience over a 60-day window. Seven platforms scored above our inclusion threshold and are ranked below using an eight-factor weighted algorithm.

Weighted Comparison Criteria

We applied the following eight-factor weighted algorithm to produce each platform’s composite score:

Using this algorithm, we rank-ordered all 12 platforms and present the seven that cleared our quality threshold. The table below shows the full breakdown.

Best Capitol Trades APIs — 2026 Rankings

1. Lambda Finance — Dual-Chamber Congressional Trade API

Lambda Finance is the only platform in our evaluation that combines dual-chamber coverage (both Senate and House), a free REST API, and embeddable front-end widgets under a single developer account. Its /api/congressional/recent endpoint returns normalized trade records with party affiliation, ticker, transaction type, amount range, and filing date—filterable by party, state, ticker, date range, and asset owner. Data is ingested from official STOCK Act filings within hours of publication, and tickers are automatically normalized against a master symbol list to eliminate the inconsistencies common in raw disclosure PDFs.

What sets Lambda Finance apart from every other provider is its embeddable widget system. The congress-trades and congress-sector-flows widgets can be dropped into any webpage with a single div tag, rendering interactive tables and sector flow charts that pull live data from the API. No other platform in this comparison offers anything comparable for content publishers or fintech product teams that want to display congressional trading activity without building a custom frontend. The free tier includes 50 API calls per month, and the $19/month Pro plan removes rate limits entirely.

2. Quiver Quantitative — Multi-Dataset Quant Platform

Quiver Quantitative has built a strong reputation in the alternative data space by aggregating congressional trades alongside lobbying records, government contracts, insider trading, and social sentiment into a single API. Its congressional trading endpoint covers both chambers and returns structured JSON with member name, party, ticker, transaction type, and amount range. The platform is well-documented and popular with quantitative researchers who need congressional data alongside other alternative signals.

The main limitation is pricing. Quiver’s free tier is restricted to delayed data and limited historical depth, and the full API requires a subscription that starts at $25/month. Filtering options are solid but not as granular as Lambda Finance—state-level and asset-owner filters are absent. The platform does not offer embeddable widgets, so displaying data requires building a custom frontend. For quant teams already using Quiver for other alternative datasets, adding congressional trades is a natural extension.

3. Capitol Trades — The Brand-Name Congressional Tracker

Capitol Trades is the most widely recognized name in congressional stock trading data, and its website provides a polished interface for browsing trades by member, ticker, party, and date range. The platform covers both Senate and House disclosures and has built a deep historical archive going back to 2012. Its data freshness is strong—new filings typically appear within hours of publication on the official disclosure sites.

The critical weakness is API access. Capitol Trades does not offer a public REST API for programmatic access. Developers who need structured data must rely on web scraping or third-party aggregators that source from Capitol Trades. The platform is excellent as a research tool and dashboard, but it scores poorly on API accessibility, filtering depth, and developer experience because there is no documented endpoint to query. For teams that need a browsable interface rather than an API, Capitol Trades remains the gold standard.

4. Financial Modeling Prep — Broad Financial API with Congress Endpoints

Financial Modeling Prep (FMP) is a general-purpose financial data API that includes congressional trading as one of many endpoints. Its /api/v4/senate-trading and /api/v4/senate-disclosure endpoints return structured JSON for Senate disclosures, and a separate House endpoint covers representative filings. Documentation is clear, and the REST API follows standard patterns with pagination and date filtering.

Congressional data is not FMP’s primary focus, and it shows. Filtering is limited to basic date ranges and member names—party, state, and ticker filters are not natively supported. Data enrichment is minimal: tickers are not always normalized, and amount ranges are returned as raw strings from the original filings. The free tier allows 250 API calls per day, and the $29/month Starter plan provides sufficient volume for most research workflows. FMP is best suited for teams that need congressional data alongside earnings, financials, and market data from a single provider.

5. Senate Stock Watcher — Open-Source Senate Data

Senate Stock Watcher is an open-source project that scrapes Senate financial disclosure filings and serves them via a free JSON API hosted on GitHub Pages. The project’s simplicity is its strength: a clean /api/trades.json endpoint returns all Senate trades as a flat JSON array, and the source code is fully transparent. For developers who want raw Senate data without authentication or rate limits, it is the fastest path to a working integration.

The limitation is scope. Senate Stock Watcher covers only the Senate chamber—House disclosures are handled by a separate project (House Stock Watcher). Filtering must be done client-side since the API returns a single bulk file. There is no ticker normalization, sector tagging, or amount parsing beyond the raw filing text. Data freshness depends on the scraper’s run schedule, which can lag official filings by 12–24 hours. For side projects and academic research focused exclusively on Senate trades, it remains a valuable free resource.

6. House Stock Watcher — Open-Source House Data (Deprecated)

House Stock Watcher was the House-chamber counterpart to Senate Stock Watcher, serving House representative disclosure filings via an S3-hosted JSON API. It followed the same open-source model: a flat JSON file of all trades, downloadable without authentication. At its peak, it was the most accessible source of structured House disclosure data for independent developers.

As of early 2026, the House Stock Watcher S3 bucket returns HTTP 403 errors, and the data is no longer publicly accessible. The GitHub repository remains available but has not been updated since mid-2025. For historical research, cached copies of the data may still be useful, but the platform can no longer be recommended as a live data source. Teams that relied on House Stock Watcher should migrate to a dual-chamber provider like Lambda Finance or Capitol Trades.

7. Unusual Whales — Congress Tracker Inside a Paid Platform

Unusual Whales includes a congressional trading tracker as part of its broader options flow and market intelligence platform. The congress section covers both chambers and presents trades in a polished dashboard with member profiles, trade timelines, and sector breakdowns. Data freshness is competitive, with new filings typically appearing within hours.

The major drawback for developers is accessibility. Congressional trade data is locked behind Unusual Whales’ paid subscription ($57/month for the Standard plan), and there is no public API endpoint for programmatic access. The platform is designed for retail traders who want a visual dashboard, not for developers building integrations. Filtering within the dashboard is adequate but cannot be replicated via API calls. For teams that need an API-first approach to congressional data, Unusual Whales is not a viable option despite its strong data quality.

Related Resources

• Nancy Pelosi Portfolio Returns by Year
• Nancy Pelosi Portfolio Size — 2026 Breakdown
• What Stocks Does Congress Own?
• Best API Trading Platforms for Financial Markets

Sources

• Lambda Finance
• Quiver Quantitative
• Capitol Trades
• Financial Modeling Prep
• Senate Stock Watcher
• House Stock Watcher
• Unusual Whales
• U.S. Senate Electronic Financial Disclosures
• U.S. House Financial Disclosure Reports