diff --git a/client/src/rpc_request.rs b/client/src/rpc_request.rs
index bd93bdd0ee..22c5d5e12b 100644
--- a/client/src/rpc_request.rs
+++ b/client/src/rpc_request.rs
@@ -102,6 +102,7 @@ impl fmt::Display for RpcRequest {
 pub const NUM_LARGEST_ACCOUNTS: usize = 20;
 pub const MAX_GET_SIGNATURE_STATUSES_QUERY_ITEMS: usize = 256;
 pub const MAX_GET_CONFIRMED_SIGNATURES_FOR_ADDRESS_SLOT_RANGE: u64 = 10_000;
+pub const MAX_GET_CONFIRMED_BLOCKS_RANGE: u64 = 500_000;
 
 // Validators that are this number of slots behind are considered delinquent
 pub const DELINQUENT_VALIDATOR_SLOT_DISTANCE: u64 = 128;
diff --git a/core/src/rpc.rs b/core/src/rpc.rs
index d210c425c5..2c192076df 100644
--- a/core/src/rpc.rs
+++ b/core/src/rpc.rs
@@ -13,7 +13,8 @@ use solana_client::{
     rpc_config::*,
     rpc_filter::RpcFilterType,
     rpc_request::{
-        DELINQUENT_VALIDATOR_SLOT_DISTANCE, MAX_GET_CONFIRMED_SIGNATURES_FOR_ADDRESS_SLOT_RANGE,
+        DELINQUENT_VALIDATOR_SLOT_DISTANCE, MAX_GET_CONFIRMED_BLOCKS_RANGE,
+        MAX_GET_CONFIRMED_SIGNATURES_FOR_ADDRESS_SLOT_RANGE,
         MAX_GET_SIGNATURE_STATUSES_QUERY_ITEMS, NUM_LARGEST_ACCOUNTS,
     },
     rpc_response::Response as RpcResponse,
@@ -576,6 +577,12 @@ impl JsonRpcRequestProcessor {
         if end_slot < start_slot {
             return Ok(vec![]);
         }
+        if end_slot - start_slot > MAX_GET_CONFIRMED_BLOCKS_RANGE {
+            return Err(Error::invalid_params(format!(
+                "Slot range too large; max {}",
+                MAX_GET_CONFIRMED_BLOCKS_RANGE
+            )));
+        }
         Ok(self
             .blockstore
             .rooted_slot_iterator(max(start_slot, self.blockstore.lowest_slot()))
@@ -3552,11 +3559,37 @@ pub mod tests {
         assert_eq!(confirmed_blocks, vec![1, 3, 4]);
 
         let req = r#"{"jsonrpc":"2.0","id":1,"method":"getConfirmedBlocks","params":[9,11]}"#;
-        let res = io.handle_request_sync(&req, meta);
+        let res = io.handle_request_sync(&req, meta.clone());
         let result: Value = serde_json::from_str(&res.expect("actual response"))
             .expect("actual response deserialization");
         let confirmed_blocks: Vec<Slot> = serde_json::from_value(result["result"].clone()).unwrap();
         assert_eq!(confirmed_blocks, Vec::<Slot>::new());
+
+        block_commitment_cache
+            .write()
+            .unwrap()
+            .set_largest_confirmed_root(std::u64::MAX);
+        let req = format!(
+            r#"{{"jsonrpc":"2.0","id":1,"method":"getConfirmedBlocks","params":[0,{}]}}"#,
+            MAX_GET_CONFIRMED_BLOCKS_RANGE
+        );
+        let res = io.handle_request_sync(&req, meta.clone());
+        let result: Value = serde_json::from_str(&res.expect("actual response"))
+            .expect("actual response deserialization");
+        let confirmed_blocks: Vec<Slot> = serde_json::from_value(result["result"].clone()).unwrap();
+        assert_eq!(confirmed_blocks, vec![1, 3, 4, 8]);
+
+        let req = format!(
+            r#"{{"jsonrpc":"2.0","id":1,"method":"getConfirmedBlocks","params":[0,{}]}}"#,
+            MAX_GET_CONFIRMED_BLOCKS_RANGE + 1
+        );
+        let res = io.handle_request_sync(&req, meta);
+        assert_eq!(
+            res,
+            Some(
+                r#"{"jsonrpc":"2.0","error":{"code":-32602,"message":"Slot range too large; max 500000"},"id":1}"#.to_string(),
+            )
+        );
     }
 
     #[test]
diff --git a/docs/src/apps/jsonrpc-api.md b/docs/src/apps/jsonrpc-api.md
index 2c992f5c80..7551979a26 100644
--- a/docs/src/apps/jsonrpc-api.md
+++ b/docs/src/apps/jsonrpc-api.md
@@ -363,8 +363,9 @@ Returns a list of confirmed blocks
 #### Results:
 
 The result field will be an array of u64 integers listing confirmed blocks
-between start_slot and either end_slot, if provided, or latest confirmed block,
-inclusive.
+between `start_slot` and either `end_slot`, if provided, or latest confirmed block,
+inclusive.  Max range allowed is 500,000 slots.
+
 
 #### Example:
 
@@ -378,7 +379,8 @@ curl -X POST -H "Content-Type: application/json" -d '{"jsonrpc": "2.0","id":1,"m
 
 ### getConfirmedSignaturesForAddress
 
-Returns a list of all the confirmed signatures for transactions involving an address, within a specified Slot range. Max range allowed is 10_000 Slots.
+Returns a list of all the confirmed signatures for transactions involving an
+address, within a specified Slot range. Max range allowed is 10,000 Slots
 
 #### Parameters: